Abstract: Microwave plasma chemical vapor deposition(MPCVD)is considered to be an important method for the high quality diamond films deposition due to its unique advantages.The electric field distribution and strength in the cylindrical single-mode cavity are numerical simulated,meanwhile the study on the plasma discharge and the diamond films deposition are carried out on the MPCVD device.The results show that the simulated maximum electric field strength of the cylindrical single mode MPCVD device is 3.0×10⁵ V/m when the input power is only 100 W,which shows that the cavity possesses excellent focusing capability,and the design of quartz window can avoids plasma etching at the same time.In addition,High quality micro and nano diamond films are obtained on the diameter of 50 mm silicon wafer.The results provide theoretical guidance for the development of MPCVD devices.