With the experiment of fuel system undergoing the boost fueling to self-suck, the study on history rate of fuel flow is conducted. Based on the experimental study and the analysis of operational principle of transient process of helicopter fuel system transferred from boost fueling to self-suck, a simulation model of helicopter fuel system is built with commercial code of Flowmaster. The simulation results and the experimental results are in a good agreement, which reveals the validity of numerical model. By combining with simulation results，the impact of check valve spring preload and spring rate on engine inlet pressure and flow rate is analyzed. Consequently, the reference of components of fuel system is provided.