Urban network and outward connections of cities are emerging directions of recent geographical researches and important aspects for policy making in Yangtze River Economic Belt（YREB），which has become a national strategy in contemporary China. Existing studies of urban network were usually based on gravity model using the population or regional GDP data as the key parameter. However，this failed to differentiate the basis function from the non-basic function of cities and may lead to biased results. This paper tries to further the research by introducing urban flow，which is a widely adopted term in China’s economic geographical studies，into the gravity model. It got some different findings from the previous studies. First，while it is believed that the middle reach area of the Yangtze River has larger urban flows than the up reach area，suggesting that some cities in the western China participated more actively in regional economic division as the frontier region connecting to the South-East Asia. Second，the rank-size of urban flows in the YREB can be better fitted by the Zipf model than the populations and follows hierarchical distribution. Third，there are three sub-regions and four clusters of network in the YREB with quite different characteristics from each other. Fourth，the centrality of Nanjing and Nanchang within Jiangsu and Jiangxi province is relatively lower than other provincial capitals. Overall，results of the gravity model based on urban flows are closer to the reality than traditional gravity models and it should be applied in more studies in the future.