Abstract: Based on field data, this paper analyzes the impact of saline water intrusion on Guangzhou waterway and identifies the dominant factors determining the variation of saline water tide. Furthermore, by the use of salinity mathematical model, the degree of effects of four factors, i. e. , terrain, sea level, wind regime and flow rate distribution on saline water tide variation, is presented respectively. Among these factors, flow rate distribution has significant effects on the saline water boundary, terrain and wind regime have less significant effects on it, and the sea level can affect the saline water tide weakly.