Is urban sprawl conducive to improving urban productivity? The paper explains theoreticaly the intrinsic mechanism of how urban sprawl affects productivity from urban scale and urban population density, and then, based on the night light data of 104 cities in the Yangtze River Economic Belt from 202-2013, empirically studies the productivity effects of urban sprawl. The main conclusions are as follows: 1)Urban sprawl has a significant negative impact on the productivity of the Yangtze River Economic Belt, which means that urban sprawl and low-density expansion hinder the productivity of the Yangtze River Economic Belt. 2)The regional study finds that urban sprawl has negative effects on urban productivity in eastern, central and western regions, has the minimum impact on productivity in the east, and has a greater impact on productivity in the central and western regions. 3)The research of the branch industry finds that urban sprawl reduces secondary productivity while significantly increasing the productivity of the service sector. 4)The Durbin model with spatial spillover efects tells that the direct and indirect effects of urban sprawl on productivity are significantly negative, and that the indirect effects are much greater than the direct, which means urban sprawl has significant spatial spilover effects on the urban productivity of the Yangtze River Economic Belt.