Nowadays，increasing attention has been paid to water transportation to achieve the goal of carbon neutrality. As an energy-saving and environmentally friendly transportation mode，water transportation plays an important role in regional transportation systems. The proportion of water transportation greatly influences the effect of energy conservation and emission reduction of regional transportation systems. From the perspective of Guangdong Province Waterway Development Plan （2020-2035），this paper focuses on the analysis of the development status and planning vision of inland waterways in Guangdong Province，predicts the change in the theoretical inland waterway transit capacity of the province，and explores the impact of the development of inland waterways on the carbon reduction in the regional transportation system of the province depending on the freight volume of its inland waterway. The results show that the upgrading of inland waterways in Guangdong greatly improves the theoretical inland waterway transit capacity and makes water transportation better share the goods transportation of highway and railway，which reduces the carbon emission of the regional transportation system in Guangdong by about 2.2%. This paper can provide a theoretical reference for the more rational construction of inland waterways in Guangdong.