Synthesis of acrylic acid-acrylate salt (acrylic acid-potassium acrylate and acrylic acid-sodium acrylate) copolymer super absorbent resin (SAR) by UV photopolymerization have many merits compared with traditional methods, such as simple technology, short reaction time, normal temperature operation and no pollution. Photoinitiator is the most important factor of photopolymerization. In this paper, several kinds of photoinitiators ( Iragure651、Iragure819、Iragure184、Iragure1700、Iragure1800 and Iragure2929) were studied, including the influence of varieties and concentration on the performance of UV copolymerization and the water absorption capacity of SAR. It shows Iragure651, Iragure1700 are efficient photoinitiators for photopolymerization of SAR. The proper exposing time for preparing SAR was about 10min. Using Iragure651 as photoinitiator, the water absorbency and 0.9% NaCl absorbency of acrylic acid-potassium acrylate copolymer SAR reach 1358mL/g and 115mL/g respectively.