There has been high risk on internet financial P2P lending platform. In order to assist investors to obtain a better loan proceeds, this paper comprehensively takes the risk of bad debts, failure of bidding, interest rate and investor risk preferences and other factors into consideration, and proposes the investment decision-making algorithm IDEA (investment Decision Analysis): building the investor-loan network, taking advantage of investment behavior of loan information in the network to measure the risk of bad debts and make use of the graph based semi-supervised learning method to metric the risk of failed bidding to provide the basis for investment decisions. Experiment results on real datasets show that, compared with existing algorithms, our algorithm can not only get a better return on investment, but also assist investors with different risk appetite to make investment decisions.