By constructing quantitative model and tradeoff/synergic model of ecosystem services, the spatio-temporal evolution process of key ecosystem services in Southwest China was investigated. Based on the spatial static and temporal dynamic scale, the relationship between ecosystem services was quantitatively measured to further explore heterogeneous characteristics of tradeoff/synergic effects between ecosystem services in southwest region and reveal the formation mechanism of ecosystem services tradeoffs under different urbanization gradient. The results showed that (1) in the past 20 years, the area of cultivated land and grassland in Southwest China decreased significantly, while the area of construction land and water increased by 141.19% and 34.6%, respectively. The urban expansion characteristics of Guizhou Province were prominent, and the reduction of cultivated land in Sichuan Province was the most obvious. Habitat quality index and water yield in the study area showed a decreasing trend, while three ecosystem services, including soil conservation, food production and carbon storage increased to some extent; (2) from the dynamic perspective, there was a significant tradeoff relationship between soil conservation and water yield, and a largely insignificant relationship between carbon storage and the other four ecosystem services, the area of soil conservation and water yield service tradeoff (61%) was larger than that of synergistic relationship (27%), and there was insignificant relationship between carbon storage and other four ecosystem services in a large area (> 70%); (3) from the static perspective, ecosystem services in different urbanization gradient areas showed significant heterogeneity. The non-urbanized area was similar to the study area as a whole, but the correlation between soil conservation and carbon storage gradually weakened. The tradeoff/synergic relationship between ecosystem services in rapid urbanization areas was the most significant. In particular, the correlation between carbon storage and habitat quality was the highest (R²=0.541). The interaction intensity between ecosystem services in past urbanization areas was weaker than those in other two areas, but any two ecosystem services all presented the positive correlation, among the 10 ecosystem service pairs, 7 ecosystem service pairs had significant positive correlation; and (4) the rapid expansion of construction land led to the decline of ecosystem services, especially the significantly negative impact on habitat quality. The interaction between ecosystem services in rapid urbanization areas was the most vigorous. The large increase in forest area led to an increase in soil conservation, especially in mountainous areas. Meanwhile, urbanization could cause a strongly synergistic decline in carbon storage and habitat quality. Although ecological protection and management projects can improve regional comprehensive ecosystem services, they will bring certain negative effects to territorial ecological restoration projects aimed at specifically increasing certain ecosystem services.