Abstract: The properties of the conventional cement slurry such as thickening time, rheology and stability cannot meet the requirement of complex technology of expansion pipe cementing and long construction time. A new type of ultra-retarding cement slurry system has been developed to solve this problem, which contains a new type retarder CH88, matched optimal filtrate reducer WJ60S and drag reducer CUSZ. And then its comprehensive properties were studied. The results show that the ultra-retarding cement slurry system can maintain perfect settlement stability in a long time under static condition, with more than 10 hours thickening time, and performs obviously thickening characteristics of right-angle. Field application results represent that the ultra-retarding slurry system was featured by stable performance, safety and convenience used in field, which can satisfy the expansion pipe cementing operation requirements.