Abstract: In order to further understand the radiation characteristics of medical diagnostic X-rays and verify the feasibility of computer energy spectrum simulation, two Monte Carlo simulation programs, EGSnrc and MCNP5, were used to simulate the X-ray energy spectrum distribution under different tube voltages and different additional filter thicknesses, and the energy spectrum database of RQR series radiation qualities was established. The results show that the energy spectrum distribution of X-ray is affected by tube voltage and filter material. In daily practice, when the anode target Angle of the X-ray equipment has been determined, the accurate setting of the tube voltage, regular monitoring of the radiation quality changes, and the necessary adjustment of the additional filtration are necessary means to ensure the consistency of the measurement results of the medical diagnostic equipment. Comparing and analyzing the simulation results of the two software, the average energy difference is less than 2%. EGSnrc has the advantages of easy use, high simulation efficiency and convenient data processing in the process of simulation calculation.