Abstract: The advertiser may lose much money in keyword auction, because its estimation of the optimal keyword bid price is inaccurate. To solve this problem, a winner probability model of keywords advertising position was formulated. Based on the model at the generalized second price auction mechanism, in an advertiser's position, the optimal bid price selected model was formulated in the game between bidders and auction. Simulation results showed that the keyword bid price selected model allows an advertiser to select an optimal bid price and gets maximum expected return in keyword auction.