diff --git a/app/account_service.py b/app/account_service.py
index a7ed0c4..b7872da 100644
--- a/app/account_service.py
+++ b/app/account_service.py
@@ -1,10 +1,10 @@
 from flask import *
 from Login import check_username_availability, verify_user, add_user, get_expiry_date, change_password, WarningMessage
 
-
 # 初始化蓝图
 accountService = Blueprint("accountService", __name__)
 
+
 ### Sign-up, login, logout ###
 @accountService.route("/signup", methods=['GET', 'POST'])
 def signup():
@@ -19,16 +19,44 @@ def signup():
         # POST方法需判断是否注册成功，再根据结果返回不同的内容
         username = escape(request.form['username'])
         password = escape(request.form['password'])
-        
-        #! 添加如下代码为了过滤注册时的非法字符
+
+        # ! 添加如下代码为了过滤注册时的非法字符
         warn = WarningMessage(username)
         if str(warn) != 'OK':
-            return jsonify({'status': '3', 'warn': str(warn)})
-        
+            return str(warn)
+            # return jsonify({'status': '3', 'warn': str(warn)})
+
         available = check_username_availability(username)
-        if not available: # 用户名不可用
-            return jsonify({'status': '0'})
-        else: # 添加账户信息
+        if not available:  # 用户名不可用
+            flash('用户名 %s 已经被注册。' % (username))
+            return render_template('signup.html')
+        elif len(password.strip()) < 8:  # 密码过短
+            return '密码少于8位。'
+            # return jsonify({'status': '0'})
+
+        has_specialchar = False
+        specialchar_list = ['+', '-', '*', '/', '_', '&', '%', ',']
+        for c in password.strip():
+            if c in specialchar_list:
+                has_specialchar = True
+                break
+        if not has_specialchar:
+            return '密码必须包含特殊字符'
+
+        has_upper_letter = False
+        has_lower_letter = False
+        for c in password.strip():
+            if c.isupper():
+                has_upper_letter = True
+            elif c.islower():
+                has_lower_letter = True
+            has_both_letter = has_upper_letter and has_lower_letter
+            if has_both_letter:
+                break
+        if not has_both_letter:
+            return '密码必须同时包含大写字母和小写字母'
+
+        else:  # 添加账户信息
             add_user(username, password)
             verified = verify_user(username, password)
             if verified:
@@ -43,7 +71,6 @@ def signup():
                 return jsonify({'status': '1'})
 
 
-
 @accountService.route("/login", methods=['GET', 'POST'])
 def login():
     '''
@@ -102,9 +129,9 @@ def reset():
         # POST请求用于提交修改后信息
         old_password = escape(request.form['old-password'])
         new_password = escape(request.form['new-password'])
-        flag = change_password(username, old_password, new_password) # flag表示是否修改成功
+        flag = change_password(username, old_password, new_password)  # flag表示是否修改成功
         if flag:
             session['logged_in'] = False
-            return jsonify({'status':'1'})  # 修改成功
+            return jsonify({'status': '1'})  # 修改成功
         else:
-            return jsonify({'status':'2'})  # 修改失败
+            return jsonify({'status': '2'})  # 修改失败
diff --git a/app/bug.py b/app/bug.py
new file mode 100644
index 0000000..556ba50
--- /dev/null
+++ b/app/bug.py
@@ -0,0 +1,47 @@
+from random import randint
+from PIL import Image, ImageDraw, ImageFont
+
+
+def get_random_color():
+    # 随机颜色RGB
+    return randint(120, 200), randint(120, 200), randint(120, 200)
+
+
+def get_random_code():
+    # 随机字符
+    codes = [[chr(i) for i in range(48, 58)], [chr(i) for i in range(65, 91)], [chr(i) for i in range(97, 123)]]
+    codes = codes[randint(0, 2)]
+    return codes[randint(0, len(codes)-1)]
+
+
+def generate_captcha(width=140, height=60, length=4):
+    # 生成验证码
+    img = Image.new("RGB", (width, height), (250, 250, 250))
+    draw = ImageDraw.Draw(img)
+    font = ImageFont.truetype("static/font/font.ttf", size=36)
+    # 验证码文本
+    text = ""
+    for i in range(length):
+        c = get_random_code()
+        text += c
+
+        rand_len = randint(-5, 5)
+        draw.text((width * 0.2 * (i+1) + rand_len, height * 0.2 + rand_len), c, font=font, fill=get_random_color())
+    # 加入干扰线
+    for i in range(3):
+        x1 = randint(0, width)
+        y1 = randint(0, height)
+        x2 = randint(0, width)
+        y2 = randint(0, height)
+        draw.line((x1, y1, x2, y2), fill=get_random_color())
+    # 加入干扰点
+    for i in range(16):
+        draw.point((randint(0, width), randint(0, height)), fill=get_random_color())
+    # 保存图片
+    img.save("static/captcha/" + text + ".jpg")
+    return text + ".jpg"
+
+
+if __name__ == "__main__":
+    for i in range(1000):
+        generate_captcha()