The influence of photoinitiators and monomers on photopolymerization property of photosensitive polysiloxane urethane acrylate oligomer (PSUA) was investigated by real time Infrared spectroscopy (RTIR). The results show that initiating efficiency of cleavage photoinitiators is higher than that of abstraction-hydrogen photoini-tiators and polymerization rate of the PSUA system using Irgacure 1700 as photoinitiator is the highest. The optimum concentration of photoinitiator 1173 has been determined to be 0.5 %~1 %. Double bond conversion of PSUA system decreases with increment of functionality of added monomer. Double bond conversion of PSUA system containing HEA or IBOA is higher than that containing TPGDA or HDDA (90 %~95 %) and former are polymerized almost completely meanwhile the one containing TMPTA only reaches nearly 80 %. Polymerization rate of the PSUA systems containing different monomers increases in the following order: TPGDA≈HDDA>HEA>TMPTA>IBOA. Both of double bond conversion and polymerization rate of PSUA system decrease with increment of monomer concentration.