The pyrolysis of UV curable polysilazane containing vinyl-thiol copolymer has been analyzed and characterized by FTIR, TGA-DTA-MS, XRD and energy spectrometry. Thermal decomposition of the UV curable copolymer occurred from 300 to 500 ℃. Many different kinds of gas molecules evolved during the pyrolysis, in which S element escaped from the copolymer as H2S, SO2 and thiofuran, with the total weight loss being 44.7 wt%. The density of pyrolysate dropped down at the beginning of pyrolysis, then successively increased, and finally reached 2.09 g•cm－3. Si3N4 crystal could be formed in the pyrolytic process at 1400 ℃ after 2 h and the crystalline degree could reach 91.3% at 1600 ℃ meanwhile. The quality ratio of the final product was m(SiO2)∶m(Si3N4)∶m(SiC)＝3∶26∶71.

Key words: polysilazane containing vinyl-thiol, copolymer, UV-curing, pyrolysis