Abstract: With regard to the problem of super-retarding of top slurry for the long-section cementation in deep well,a new type of retarder BCR-260L was developed.Through lab experiment,the retarding performance,strength development of cement with huge temperature difference,salt-resistance performance of BCR-260L was evaluated.The results indicated that,its performance under high temperature condition is good with a wide application range of temperature,which could satisfy the demand for the cementation under the circulating temperature of 70-180 ℃.Based on the requirement of field for slurry thickening time,the addition of BCR-260L could be adjusted to regulate the thickening time of slurry.BCR-260L has little effect on the strength development of set cement at the late stage.The strength develops rapidly under huge temperature difference,which could ensure the development of strength of the top slurry.The salt-proof capacity of BCR-260L is enough to resist 15% concentration of salt.The field application indicates that BER-260L could effectively solve the problem of super-retarding of top slurry under the huge temperature difference,it can be used widely in the future.