To research the influence of seawater intrusion when the new navigable lock is used in Jinhuigang waterway,a three-dimensional numerical model is established based on the saltwater convective diffusion theory,and the verified model is used to simulate the process of seawater intrusion into the inland river in the form of heavy flow through the new navigable lock.Based on the average salinity,salt water intrusion distance,salt water exchange rate,the anti-salt effect of the new navigable lock is analyzed.The results of simulation and analysis show that seawater intrusion gradually invades the lock chamber and inland river during the process of dilution and mixing with freshwater,and the average salinity of seawater decreases with the increase of intrusion distance.With the salt deposition in the salt-collecting area,the seawater upstream velocity gradually decreases.The seawater intrusion distance is basically stable after a period of operation of the facility,and the salt exchange rate gradually tends to be dynamic equilibrium.The new navigable lock adopts the anti-salinity measures of salt collecting area and runoff flushing,which can further enhance the anti-salinity effect of the new navigable lock.The research results can provide scientific basis for the design and application of the new navigable lock in the direct waterway of river and sea.