The cross-linking and pyrolysis of Polysiloxane (PSO)/Divinylbenzene (DVB) is investigated in this paper. It is found that only catalyzed with H₂PtCl₆ PSO/DVB can cure completely. When cured at 120℃ for 6hrs with H₂PtCl₆, the ceramic yield of PSO/DVB, the mass ratio of which is 1∶0.5, is 76%. The viscosity at room temperature of PSO/DVB and the contact angle between PSO/DVB and carbon fiber are 10.5 mPa?s and 34 degree, which make PSO/DVB very good for the preparation of three-dimension-braided fiber reinforced ceramic matrix composites. The XRD results indicate that there are SiO₂ and β-SiC microcrystals in the product pyrolyzed at 1000℃ and 1200℃, which grow markedly above 1200℃. The content of Si, O, C in the product pyrolyzed at 1000℃ is 38.33wt%, 27.33wt%, and 34.34wt%, respectively. Most C existed as free carbon, and the rest randomly mixed with Si, O to form［Si(O,C)₄］which are converted is to［SiO₄］and［SiC₄］above 1200℃.