China International Import Expo（CIIE）is a key measure of high-level opening to the outside world. It has been successfully held for 4 consecutive sessions，and its scale has gradually expanded，which effectively promotes the formation of an open world economic and trade pattern. Based on the typical data of CIIEs，this study analyzes the policy effects of the CIIE in expanding opening up from multiple perspectives，such as building a platform for economic and trade cooperation，relaxing market access，reducing tariffs，optimizing the market environment，and supporting the development of digital trade，which summarizes the successful practice of CIIE.