Literature on using firm relationship to study urban networks has been increasing in recent years. The spatial and organizational structure of firms are being widely used to build intra-firm linkages to study urban networks. In contrast, this study proposes an alternative way to establish urban networks based on real inter-firm investment data through digging out all possible linkage routes between each two firms, and chooses China’s Yangtze River Delta as study case. The results show that cities’ performance on inflow and outflow of investment vary dramatically. In particular, Shanghai, Hangzhou and Hefei hold dominant positions in the investment network. Nanjing’s network position is somewhat lower than its economic status. In terms of cities’ betweeness centrality, Shanghai stimulates the area’s integration process while Hangzhou and Hefei play the role of “bridge” between Provincial Cities and Shanghai.