High-speed railway strategy is China's national strategy, many provinces and cities step into the high- speed railway era with the opening of high-speed railway. What is the impact of high-speed railway on the quality of urban economic development in China? This paper takes Jiangxi Province as an example and analyzes the impact of high-speed railway on the economic development quality of every district in Jiangxi Province by using difference in difference model (DID) based on the data of 11 districts in Jiangxi Province from 2010 to 2016. The research shows that high-speed railway has a significant positive impact on the proportion of tertiary industry along the city,implying that high-speed rail is a very important factor to optimize the quality of urban economic development. In addition, the urbanization level of an area, investment structure, import and export structure and employment structure significantly affect the quality of urban economic development.