In this article, the analysis is made on the current cementing status and the causes of poor cementing quality in the western region of Yanchang oilfield. Based on the analysis, the slurry performance requirements for horizontal well cementing in this area are put forward. The optimized cement slurry system suitable for this area is selected, which has low filtration, zero-free liquid and high sedimentation stability, and its rheology is beneficial to improve the displacement efficiency; andefficiency; the formed cement stone has no shrinkage, micro-expansion and early strength characteristics, which can meet the requirements of horizontal well perforation post-fracturing and other projects construction. By all the above, a complete set of cement slurry system suitable for horizontal well cementing in the western area of Yanchang oilfield is formed.