To study the law of regional port system is great significance, both in theory and practicae. The main purpose of this research is to study the regional differences and dynamic evolution of the size combination and spatial structure of the Changjiang River port system in Anhui Province.By calculating the concerned statistics, the author holds that there are obvious regional disparities of port distribution and its size not only between the south and north banks but also among sub-regions. The regional differences of the size combination and spatial sturcture of the port system and their causes are analysed with the aid of multiple-regression analysis in which 16 counties and cities along the Changjiang River in Anhui Province are as the cases. Calculated results show that the cause of formation is mutual interaction between the law of port development and four economic factors-level of urbanization, communication condition, total output value of industry and agriculture and industry output value per capita in the cities.The development and changes of the port system could be divided into three stages. 1 Embryonic stage, from the end of the Ming Dynasty to the middle of the Qing Dynasty, the port system did not exist hierarchies and its spatial structure was characterized by a stable decentralized state. 2 Initial forming stage, after the middle of the Qing Dynasty it had single rank hierarchies and a unstable centralized spatial state. 3 Forming stage, since the 1950s the port system’s evolution has been characterized by multiple hierarchies and a more centralized spatial structure.Using the Gini coefficient, it can be seen that port traffic has generally become more concentrated from 1985 to 1995. During this time, however, deconcentration to some extent also existed sometimes.