我是用JSP的,,至于ASP不清楚. 在用户看到验证码的页面里有句: <script>document.write("<img border=0 src=image.jsp?rand="+Math.random()*10000+">" ;</script> <%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %> <% // 在内存中创建图象 int width=60, height=20; BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); // 获取图形上下文 Graphics g = image.getGraphics(); // 设定背景色 g.setColor(Color.white); g.fillRect(0, 0, width, height); //画边框 g.setColor(Color.black); g.drawRect(0,0,width-1,height-1); // 取随机产生的认证码(4位数字) String rand = request.getParameter("rand"); rand = rand.substring(0,rand.indexOf(".")); switch(rand.length()) { case 1: rand = "000"+rand; break; case 2: rand = "00"+rand; break; case 3: rand = "0"+rand; break; default: rand = rand.substring(0,4); break; } // 将认证码存入SESSION session.setAttribute("rand",rand); // 将认证码显示到图象中 g.setColor(Color.black); g.setFont(new Font("Times New Roman",Font.PLAIN,18)); g.drawString(rand,10,15); // 随机产生88个干扰点，使图象中的认证码不易被其它程序探测到 Random random = new Random(); for (int i=0;i<88;i++) { int x = random.nextInt(width); int y = random.nextInt(height); g.drawLine(x,y,x,y); } // 图象生效 g.dispose(); // 输出图象到页面 ImageIO.write(image, "JPEG", response.getOutputStream()); %> 上面是产生图片的JSP文件,我觉得思想也一样,参考参考