Abstract: microwave plasma chemical vapor deposition(MPCVD) system ususlly is deemed to make high gualitydiamond fims and wafers by people ,which is important technique.But，at present,because lacking of this technique,we don’tcontent with this phenomena about the need of high guality diamond fims and wafers.In this article,the primary task is to designelliposoidal microwave plasma reactors which made of stainless steel and to optimize leading dimension.For in contrast with thecylindrical microwave plasma reactor ,the same condition consist of the same input fruquency and same input power is choosed,by comparising with cylindrical microwave plasma reactor,it is conclusion that the structure of elliposoidal resonantcavity is better than the cylindrical structure .It have more advantages.