By analyzing the C2C sales records , we find the repeat purchase frequency of customers is power law distribution , which is different from the result of existing repeat purchase research that the purchase fre quency is negative binomial distribution. Based on actual situation in C2C transactions , a repeat purchase model with buying reinforcement is built , which explaned to the phenomenon of the power law distribution. Our model and empirical analysis show that , in C2C environment , the distribution of customers ’ repeat pur chase frequency is composed of a long tail and short head , meaning that a large number of customers have a low number of purchases , while a few customers have a high repeat purchase frequency. Our model also re veals that the huge number of potential customers and the repeat purchase with buying reinforcement contrib utes to the power law distribution characteristics of repeat purchase frequency.