An acid thickening agent P(AM-DMC-APEG) was synthesized by acrylamide, methacryloxyethyltrimethyl ammonium chloride and allyl polyoxyethylene ether that was with a long chain temperature-sensitive group. The optimal conditions were as follows: monomer concentration 40%, monomer ratio 1:20 :2(APEG:AM:DMC),initiator concentration 0.08%, polymerization temperature 70℃, polymerization time 3.5h. Then molecular structures and molecular weight were characterized respectively by infrared spectrum and static light scattering. After evaluation on temperature sensibility and retarding performance, the results showed that the synthetic P(AM-DMC-APEG) presented good temperature sensibility and retarding performance.