Eco-tourism competitiveness of southwestern mountainous area is the key point of the construction of mountain ecological culture. Taking Xichang city as the research area, the statistical data from 2008 to 2017 were selected, and 12 indicators were selected from four aspects of tourism resource competitiveness (TRC), tourism constitutes competitiveness (TCC), tourism infrastructure competitiveness (TIC) and tourism social competitiveness (TSC), to build Xichang ecotourism competitiveness (ETC) evaluation index system. The index weight was calculated using Mean Square Deviation and the ecotourism competitiveness was calculated by linear weighting method. The results showed that : (1) the ETC of Xichang city had been strengthened during last decade; (2) the TCC, TIC and TRC in Xichang had been continuously improved in the past ten years; (3) During last decade, Xichang's TRC had only been strengthened since 2014. To better enhance the ETC of Xichang mountain city, the utility of tourism resources should be explored and enhanced continuously in the future, to promote the construction of ecological civilization in mountainous areas of southwest China.