The crosslinked products of polycarbosilane were heated between 200-400℃ before pyrolysis in order to investigate their effects on conversation of ceramic. It was shown that 73.9% ceramic yield was raised when heated two hours at 400℃.The dominating defects in structure of its product pyrolysed were pores,not cracks in structure of that without heat-treatment.The damage of fiber could be decreased significantly if such ceramic were used as base.