Abstract: UV absorption of novel photoinitiators has been investigated by time-dependent density function theory. The reason for red shift of BDPB compared to BDMB is analyzed by frontier molecular orbitals,conjugated effect and electronic effect. Solvent effect is also studied for BDMB and BDPB. It is found that BDPB has a better photoinitiation activity than BDMB,which is a more prospective photoinitiator. Although the conjugated effect of BDMB is better than BDPB,the electronic effect is stronger on BDPB. That is a fundamental reason for red shift. It is benefit to synthesize more efficient photoinitiator that para-position of benzene near carbonyl is substituted by electron donor groups. The maximum absorption becomes red shift on polar solvent compared to nonpolar solvent.