Abstract: A key task for a search engine advertising system is to determine what advertisements should be displayed，and in what order，for each query received.This is a gaming process between advertisers and search engine：the engine needs to accurately estimate the click-through rate of advertisements，improves its revenue and satisfaction of advertisers and users.Advertisers need to guess engine ranking model，bid advertising slots，adjust strategies according to the advertising effects and perform other search engine optimizing actions.This paper guesses and conducts a common CPC mode search engine advertisements ranking method，and applies this method on guilding advertisers’ keyword selecting strategy.

Key words: web advertising, search engine optimizing, pay for searching

摘要： 搜索引擎广告系统的核心任务是针对用户提交的每个查询，决定以何种顺序显示哪些广告。这是广告商和搜索引擎之间的一个博弈过程：搜索引擎需要准确地估算广告的点击率，提高广告收益、广告商的满意度及用户的满意度；广告商则需要猜测搜索引擎的排序模型、竞价广告栏并依据广告效果调整广告策略以及执行其他的搜索引擎优化动作。探讨了推测CPC模式下搜索引擎广告排序模型的一般方法，并据此指导广告商的关键词选择策略。

关键词: 网络广告, 搜索引擎优化, 付费搜索