Abstract: This paper introduces a new method of gait representation and an improved Bayesian classification algorithm based on it at the same time.A triangle is applied to simulate the legs of key frame which has the maximal or minimal step，and extracts its parameters as the gait feature.KNN and a new N-best algorithm are used for test-data search the optimal numerical value from training data before Bayesian classification.The experimental results on the NLRP database show that the new method is not only simple and fast but also effective.