Abstract: After 2000, the focus of China's poverty alleviation work shift to the central and western regions. Yunnan is the province with the most poverty-stricken key counties which spans four linked areas along its northwest border. In recent years, the state has launched targeted poverty alleviation in key poverty-stricken counties in Yunnan province and implemented a series of preferential poverty reduction policies. By collecting country level panel data from 1995 to 2017 and using DID model, the research shows that China's poverty alleviation policy has significantly promoted the economic development of the poverty counties in Yunnan province, but the policy of the key counties is not ideal in improving the income of those poor population. At the same time, the policy effect has a serious lag, but with the policy of key counties advancing year by year and the adjustment of national poverty alleviation strategy, the policy effect of poverty alleviation and development of key counties becomes more and more obvious. At present, Yunnan province's poverty alleviation measures should not only focus on short-term poverty alleviation, but also on long-term poverty alleviation by mechanism construction.