Abstract: The southwestern mountainous cities are characterized by complex topography and geomorphology, sensitive ecological environment, tight urban construction land, high population density, and relatively lagging economic development. Urban development and construction are greatly restricted. To provide a reference for the more scientific formulation of urban development planning, the suitability evaluation of construction land and the carrying capacity evaluation of land resource based on the mean square error decision-making method in the representative mountainous city of Jinyang county in the southwestern region, were carried out.The results showed that land suitability score was 7.87, which was suitable for the construction area. The land resource carrying capacity had gradually decreased from good state to crisis state in the decade from 2007 to 2016, and land resource carrying capacity sharply decreased during the period from 2008 to 2009 due to the population increase. In the evaluation of land resource carrying capacity, the land resource carrying potential were positively correlated with the carrying capacity of land resources, and the overall trend showed a downward trend; The land resources carrying efficiency was negatively correlated with the carrying capacity of land resources, and the overall trend was upward. The suitability of construction land in urban area was good, but the edge of urban area was poor. Two suggestions were put forward：Accelerate the construction of the new city, and carry out reasonable population planning and population evacuation for the old city; Pay attention to the protection of land resources, especially the planned use of suitable land for construction, to achieve the purpose of sustainable development.

Key words: mountainous city, carrying capacity of land resource, suitability of construction land, Jinyang county