Preventing and mitigating major risks， especially reducing local government debt risks，is a new requirement put forward by the 19th CPC National Congress. For a long time，urban space has expanded extensively and its structure has become unbalanced， resulting in increasing systemic risk of urban debt， which presents an outstanding issue in the field of urban planning and construction. Selecting panel data of 272 prefecture-level cities nationwide from 2005 to 2017， this paper builds an econometric model to analyze the relationship between urban spatial structure and local government debt on the scale of three major regions of the east，middle and west and on the scale of large，mediumand small cities. The results of the study show that urban land expansion， urban population density changesand urban land use structure have a significant impact on local governmental debt ratio. Accordingly，recommendations are proposed for constraining space expansion，regulating population density and optimizing land use structure to optimize government debt.