The automotive foundry industry is still facing greater challenge to make casting component lighter, stronger, tougher and cheaper. As computer process simulation technology has become a very helpful tool, more and more companies are popularly applying this tool in their optimizing casting structure and casting process designs. Fighting against casting defects is usually one of the major subjects in optimizing both casting structure design and casting process design. Computer simulation can reasonably predict “casting results” based on the structure/process data designed for a casting component previously or even conceptually. This prediction can provide us with some information about castability of a casting structure and then allow us to recommend for further improvement in its “original structure design” or to make a better casting process design to minimize the risk, i.e., those potential casting defects. For such purpose, a very important step is that computer process simulation must be performed before, not after, a casting is poured on the floor. This is an efficient way and also a successful way in improving casting quality, and reducing casting scrap and production costs.In this paper, some experiences as well as several examples in applications of computer simulation for automotive castings are presented. By combining the casting experience with computer simulation technique, both casting structure and casting process designs such as casting orientation in mold, gating/risering designs, and many metallurgical factors in foundry operations can be optimized.