By collecting relevant data of information disclosure in the official website of P2P online lending platforms, this paper uses correlation analysis to screen out 10 indicators to build a credit rating system. Combining the entropy method to weight the indicators, a simple and applicable credit rating model was constructed to rate the platform. Taking Paipaidai established in 2007 as the empirical object, we find out that the final rating result of Paipaidai was 92 points, and the corresponding grade was AA, which verify the operability of the P2P credit rating system.