Abstract: In order to study fuel suction characteristics of a fuel pump, a simulation model of a fuel pump is established by the software AMESim. Taking a fuel pump of an underwater vehicle for example to conduct simulation, the results accord with the experimental data. Based on the simulation results, the influences of inlet pressure and rotational speed on inlet flow rate are analyzed, and the critical relation between inlet pressure and rotational speed is achieved with genetic algorithm taking no air release in the piston chamber as an objective function. Simulation results show that the pressure in cylinder chamber approaches the minimum at about 270° of rotational angle, where the piston is in medium of fuel suction process; and if the inlet pressure is lower or rotational speed is higher than their critical values, the minimum pressure in piston chamber gets lower than the separation pressure of air, as a result, fuel releases air to generate cavitation, hence the inlet flow rate becomes significantly lower than the theoretical value.