By orthogonal design strategy, PCS with a super high molecule weight was synthesized under high pressure from the PCS with a low/middle molecule weight synthesized under normal pressure. Its structure and performance were characterized by FTIR、GPC and NMR. It was found that suitable reaction condition should be 6 hours at 460℃ to 470℃ and under 1MPa to 2MPa beforehand. Average molecule weight of the synthesized PCS was 6400 to 8500. Both its degree of branching and its content of Si-H bond decreased slightly compared with the material PCS. The average molecule weight of PCS with a super high molecule weight could be adjusted preferably by means of controlling reaction time.