The problem of customer churn in Non-contractual setting is rising more and more attention. As typical of this setting – E-commerce sites, because of its specificity makes more difficult to judge customers churn in this site. Pareto / NBD model is to forecast customers repeat purchase behaviours ,which is the first model that takes into account of customer churn in Non-contractual setting. By predicting P (active), it is better to solve customer churn prediction. In this paper, using Pareto / NBD model as based model to empirical study in e-commerce site and also test and verify the validation of the Pareto / NBD to solve customer churn problems in Non-contractual setting.