Abstract: Conventional cement slurries in thief formation were difficult to solve some questions,such as,lower upward height of cement and the cement mantle brittle rupturing by perforation and subsequent stimulations,so the leak protection and toughness-reinforcement cement slurry was developed.Leak protection and different mechanical properties of this slurry,such as fracture resistance,shock resistance and engineering practices were studied,and did the simulated test of shaped charge perforation,blended ash consistency refining surface and well cementing.the.Laboratory researches and field tests indicate that F27A Leak Protection and Toughness-reinforcement Cement Slurry had effect of high plastic,impact resistance and lost circulation protection,and could meet the demand of field operations.the fiber toughness cement slurry system was applied in 8 wells in Zhongyuan Oilfield and got great success.The cost of cementing can be decreased effectively.