The Main Guide Star Catalog for the China Space Station Telescope (CSST-MGSC) is an essential resource that provides comprehensive coverage of the sky and encompasses potential objects that can be utilized as guide stars for FGS. The CSST-MGSC plays various roles in different stages of the CSST mission. It serves as a fundamental tool for verifying the effectiveness of the sky survey strategy, facilitating the simulation of guide star images, and enabling research on sky survey strategy algorithms. Furthermore, it acts as the input for generating both the Uploaded Guide Star Catalog and the On-board Guide Star Catalog when the CSST is in orbit.