The importance of ecological conservation is a comprehensive index representing the importance of ecosystem structure and ecosystem services. Based on the analysis of natural environmental characteristics and the key ecological problems in southwest China, this study constructed an index system of ecological conservation importance by a comprehensive consideration of ecological sensitivity and ecosystem service, as well as the application of a GIS platform. In addition, the article also discussed spatial distribution features and their significance. The results showed that the area of extreme importance is 757200 km². It is mainly distributed in the Yarlung Tsangpo river basin, Hengduan Mountainous, and Western Sichuan Plateau. The area accounts for 32.5% of the southwest area, providing 59.4% of the soil conservation, 54.5% of the water retention, and 69.7% of the attentive protected species. The results suggest that the extremely important areas act as an ecological protection redline and should be strictly protected to maintain ecological security and promote sustainable development in southwest China.