Polycarbosilane (PCS) of high molecule weight was a kind of important precursor for SiC fibers with low oxygen content.High molecule weight PCS was synthesized under high pressure by using PCS of low/middle molecule weight synthesized under normal pressure.The structure and performance of the products were characterized by means of FTIR
GPC and NMR measurements.PCS samples of weight overage molecular weight 6400~8500 and less degree of branching were obtained.The suitable conditions for preparation are as follows:reaction time 6 h