Abstract: This paper reports the analysis and identification of the pyrolysis species of plasma polymer of vinyltrimethylsilane (VTMS) with Ar, N_2and benzene (Bz) mixture system by means of PGC-MS. The PGC-MS results have indicated that the pyrolysis products of plasma polymer of VTMS/Ar, VTMS/N_2 and VTMS/Bz three systems consisted of 8, 10, and 16 main compounds, respectively. According to the PGC-MS data, the chemical structure of plasma polymer of VTMS is discussed, and the reaction mechanism is deduced for plasma polymerization of VTMS.