This paper divides the economic operating system of peer-to-peer online lending industry into industry subsystem, investment and financing subsystem and macroeconomic subsystem. By establishing a system dynamics model and conducting simulation analysis, this paper explores the influence and trend characteristics of the monetary policy, regulatory policies and investment and financing expectations to China’s P2P industry development. Tight monetary policy promotes the development of the P2P industry in the short term, but it reduces the scale of the industry in the long run. A strong regulatory policy leads to an outbreak of industry risks in the short term and stabilizes the industry in the long run. Changes in investment and financing expectations make the scale experience the process of falling, slight rising to rapid decline. Based on the simulation results, the policy enlightenment and suggestions can be obtained to promote the steady development of P2P online loan industry.