Abstract: In accordance with the feature of P2P botnet, the Hidden Markov Model has application in P2P botnet detection.Firstly, according to the situation and problems of the botnet recently, the life cycle and behavior characteristics of the P2P botnet have been analyzed.After that a mathematical model has been built to describe the P2P botnet with the Hidden Markov Model in state division of the bot.Meanwhile, a method of P2P botnet detection has been proposed.Finally, we analyzed and summarized the experimental results, and verified the reliability and rationality of the detection method.