Abstract: The usage of verified code is to distinguish between human and machine behavior，which can be used to prevent the malicious behaviors of web robot.The emergence of verified code also makes a number of new types of jobs.The development of e-commerce needs a certain way to promote its goods，and disabilities need urgent attention;thus，many people begin to study web robot technology.They hope that it can realize automatic registrations for email systems，multi-send messages，automatic flood-blogging and auto-login et al.At present，various types of web systems make use of verified code to prevent robots invasion，so the verified code recognition technology is a research hotspot.Based on SVM（Support Vector Machine），a verified code recognition algorithm is proposed，and the experimental results show that the algorithm is efficient.

Key words: Support Vector Machine（SVM）, Sequential Minimization Optimization（SMO）, working set selection, kernel function, multi-class classification, verified code recognition

摘要： 设计验证码的主要目的是区分人类和计算机，用来防止网络机器人的一些恶意行为。验证码的出现也催生了一批新工种，电子商务的发展迫切需要一种推广方式来推销他们的商品，残障人士上网问题也需要迫切关注，因此许多人开始研究网络机器人技术，用来实现邮箱自动注册、群发信息、自动灌水、自动登录等功能。目前，各种类型网站系统都利用验证码阻止网络机器人入侵，从而验证码识别技术成为研究热点。基于SVM技术对图像验证码进行识别，取得了良好的效果。

关键词: 支持向量机, 序贯最小化算法, 选择工作集, 核函数, 多类分类, 验证码识别