Dataset with missing values is quite common in real applications.It is a big problem of data pretreatment,and handling missing values has become a research hot issue.EM chooses the center of cluster randomly leading to cluster irregularly,so this paper uses the result of Nave Bayesian as the initial range of EM,then refines the value reduplicative,finally gets the excepted maximize value.The research result suggests that this algorithm improved the level of cluster and had a better data make-up result.