Realizing the ideal of digital urban design needs to be based on data-based empirical research, and the working method of applying research results to design. In this paper, we take the urban renewal project of Gaochun Old Street Historical Commercial Street in Nanjing, which was built in the Song Dynasty, as an example. It describes how to comprehensively utilize the results of spatial syntax modelling and commercial business density correlation calculations, and spatially analyse these data in the deepening stage of the urban block-scale design scheme. The conclusions are also applied to auxiliary design work such as base potential assessment, scheme comparison and optimization. (1) The high value areas of integration, penetration and connectivity parameters of the road network in commercial neighbourhoods are clarified, and the cluster clustering phenomenon of commercial business distribution is found. (2) The differences in the calculation results of the three algorithms under the same road network structure were compared. (3) Each type of correlation characteristics of the two were calculated to see if they are significantly positively correlated. Among them, the integration degree and selectivity of the road network were significantly positively correlated with the density of commercial buildings of shopping, accommodation and catering types, but the correlation with the density of commercial buildings of living types was weak. (4) Based on the degree of dependence of each commercial type on the road network, new renewal and protection strategies are proposed for the current spatial characteristics and commercial layout of urban block, in order to promote the synergistic development of business and tourism.