Due to its characteristics of nearby power generation, grid-connection, conversion and use, rooftop photovoltaic power generation has formed the advantages of less investment, flexible, efficient and environmental protection, with broad prospects for development. Therefore, studying its economic performance is of great significance to investment decision and policy improvement. Under the current technical cost and policy conditions of rooftop photovoltaic in China, this paper constructs a cost-benefit analysis model considering the impact of inflation on cash flow. The results show that: For small rooftop photovoltaic in China, first of all, under the existing subsidy price and cost, its investment payback period is short and the risk is low. Secondly, the average internal rate of return is more than 10%, and the levelized cost of electricity is 0.2727–0.5573CNY/kWh, so the economic performance is good. Then, although the subsidy price has been lowered twice in a row in 2018, its economic performance is still relatively good. Finally, in the economic performance analysis of rooftop photovoltaic, besides the influence of power generation capacity, loan interest rate, construction cost and other factors, the time value of capital and inflation are also factors that cannot be ignored.