Abstract: The 2.45 GHz microwave plasma chemical vapor deposition (MPCVD) system has been able to deposit diamond films with diameters exceeding 60 mm.Due to the semi-spherical distribution of plasma in MPCVD system,it is difficult to guarantee the uniformity of the deposited large-scale films.This problem can be solved to some extent by adjusting the plasma distribution.Based on simulation,it is found that the hollow cathode discharge can be formed by the gap generated by the substrate edge suspension,which can improve the deposition rate of the edge film and optimize the uniformity.The test results showed that the thickness variance valve of 80 points on the 100 mm diameter diamond film decrease from 4.5×10^-4 to 5.0×10^-5,which means that the film uniformity is improved.The thermal stress distribation on the surface of the diamond film is more uniform,and thichness extreme valve difference is reduced from 70μm to 30μm,which reduces the possibility of cracks in the film during griding and polishing.At the same time,the film growth uniformity and film quality are improved at lower deposition pressure and thickness extreme valve difference is only 10μm.