Polyurethane-Type polymeric photoinitiators containing side-chain thioxanthone and in-chain coinitiator amine were synthesized through step polymerization of diisocyanate, 2-(2, 3-dihydroxy)propoxy-thioxanthone (HPTX) and N-methyl diethanolamine. The thioxanthone and coinitiator amine structures were successfully introduced into the backbones of polymeric photoinitiators. FT-IR and 1H NMR analyses confirmed the structures of polymeric photoinitiators. UV-Vis spectra showed the macromolecular chain have no obvious effect on the maximal absorption of thioxanthone moieties. Photopolymerization of polyurethane acrylate resin (PUA), initiated by Polyurethane-Type polymeric thioxanthone photoinitiators, was studied through photo differential scanning calorimetry (photo-DSC). The results indicate that PU-IMTX is the most efficient photoinitiator for the photopolymerization of PUA among the photoinitiators synthesized in this article.