Abstract: In the Dingshan Block, shale formation has the characteristics of high temperature, high formation pressure and fracturing pressure due to its deep burial depth. Therefore, cementing issues for deep shale gas horizontal well should be considered carefully to meet the requirement in staged fracturing and long-term production. Towards those difficulties in cementing of deep shale formations, numerical simulations was done to analyses cement mechanical properties to meet the demand in staged fracturing. In addition, high strength flexible cement slurry system was developed, and pad fluid for oil flushing was optimized to improve its heat resistance and wettability. Laboratory experiments showed that the flexible cement slurry system temperature resistivity could go up to 140 ℃, with modulus elasticity 4.5 GPa and set cement permeability 0.07 mD. Flushing efficiency reached 100% in 7minutes after pad fluid temperature went up to 140 ℃. This system and supporting processes were applied in Well Dingye2-HF and resulted in excellent cementing quality with over 96% of satisfactory intervals in the first interface, which ensured the integrity of cement annulus under fracturing pressure of 105 MPa.The application demonstrated that the optimized flexible cement slurry system, pad fluid system and matching processes could meet the demand of cementing in the Dingshan Block, and provided reference for deep shale gas horizontal well cementing.