Market segmentation is a common phenomenon，which is the main obstacle to the development of urban agglomerations in China. Sichuan’s four major urban agglomerations are in the critical period of formation. It is urgent to break the market segmentation and promote market integration among cities. At present，relative price method is the mainstream method to measure the degree of market segmentation. The analysis of Sichuan Province shows that the degree of market segmentation among cities is in a state of fluctuation，and the trend of change is consistent with the economic growth rate and urbanization growth rate. In recent years，under the downward pressure of economic growth，the degree of market segmentation among cities has entered a new upward trend. Because of the fierce competition among the cities，the market segmentation of the southern urban agglomeration has been at a high level for a long time，while the Chengdu Plain urban agglomeration has entered a stable period. Therefore，further clarifying the government’s function orientation，improving infrastructure and improving the quality of system supply are the key points to promote the development of Sichuan urban agglomeration.