The comprehensive development of coastal areas has now risen to national development strategic level, the coastal port construction is carried out rapidly. On the basis of the relationship between ports and hinterland, this paper analyzes many factors which possibly influence Jiangsu coastal port cargo throughput and picks up the most important factors by principal component analysis in the past ten years. This paper also probes into the inherent mechanism of impacts of port throughput, and puts forward a forecast model based on the above mechanisms. Furthermore, this paper applies the model in the test of port throughput in Nanjing port and it provides an effective data support for the new development of Jiangsu coastal ports.