Abstract: By studying the densification process of the same height, different diameter and the same diameter , different height preforms, we examined the effects of preform geometry on radio frequency assisted chemical liquid vapor deposition(CLVD) of carbon preforms. There is an optimal diameter among the same height, different diameter preforms. The deposition pattern of this diameter preform is from inside to outside. The carbon/carbon composite made by this preform has the highest density and the smallest open porosity. As the height decreased, the deposition pattern is first from the center to the two sides, then from inside to outside, finally from outside to inside. The apparent density of the h =70mm sample is the highest, and the open porosity of it is the smallest.