Based on the medium and remote planning on space solar power satellite (SSPS) and technological development level in China, the transmitting antenna aperture is estimated to be about 200 m in the future. According to the constrains of transmitting and receiving antenna aperture, with respect to contradiction between beam collection efficiency and construction cost that are both associated with receiving antenna aperture, a receiving antenna aperture optimization process is given by studying power density distribution in receiving antenna with different sizes and analyzing the corresponding back end rectifying circuit requirements. Research results show that the reasonable size of receiving antenna in MW-level SSPS system is 5 km, while only type of diode and the same rectifier are adopted in the whole antenna area. This parameter supplies technical support for the realization of MW-level SSPS demonstration and verification system. On the basis of this, the implementation of rectification circuit is studied. Finally, feasible techniques for MW-level SSPS of lower power density are proposed.