Casting valve bodies serve as critical components of hydraulic valves. The quality and performance of hydraulic systems are highly important for ensuring their reliability, stability, and service life. With the continuous development of industrial technology, the requirements for hydraulic valves in various industries are increasing daily. To improve the stability of the casting process of the casting valve body and adapt the product to more complex high-pressure, high-temperature, and high-corrosion working conditions, a casting model of the valve body was established. The casting process was simulated through the numerical simulation software ProCAST. The causes of shrinkage porosity and shrinkage cavity defects have been discovered. The volume of shrinkage holes and porosity defects is reduced by measures such as optimizing the runner, setting risers, and placing chill irons. The results show that the shrinkage hole and porosity defects of the improved castings have been effectively controlled and that the defect volume has been reduced by more than 95%.