Abstract: Based on the characteristic analysis of the structure of the in-line engine cylinder body, the step pouring system with anti-direct pouring channel was designed, the cylinder block mold was placed upside down in the cavity, and riser and exhaust rod were placed on the side. Then the mold filling process, solidification process, temperature distribution and defect distribution of the casting were simulated and analyzed by ProCAST software. Finally, the process was applied to the trial production of cylinder block. The metallographic observation, performance test and defect detection were performed. The results show that the quality of the actual produced cylinder body is good, all properties meet the requirements, and the numerical simulation has good agreement with the actual production.