High pressure pump in diesel engine high pressure common rail fuel injection system was studied.The common rail system structure and working principles were introduced.Using GTFuel analysis software，the simulation model of the high pressure pump was established.The impacts of the spring stiffness，preloaded and plunger diameter of high pressure pump on the injection characteristics were analyzed.The simulation results show that:the spring stiffness and preload have almost no effect on the fuel injection pressure，injection rate and injection quantity,and the plunger diameter has different effects on the injection pressure at different injection period.The simulation data provide theoretical basis and practical value for the common rail design，produce and simulation.