Abstract: The effects of pressure on the deposition of diamond films is based on simulation and simulation were systematically investigated in a 10 kW home-made MPCVD apparat in a certain high-power environment.The surface morphology of the diamond was analyzed by SEM and the crystal quality and FWHM of the diamond films were analyzed by Raman characterization.The results show that pressure has a great effect on electron density，which in turn affects the surface morphology of diamond-deposited films.Under the microwave power of 5 kW，17 kPa is the optimum deposition pressure，the deposition morphology is the best，and the half width is the minimum.When the pressure is lower than 17 kPa，the quality of the crystals increases with the increase of the pressure.When the pressure exceeds 17 kPa，the quality of the crystals does not increase or decrease.