The invention belongs to the technical field of the water ecological environment, and particularly to a device and a method for stimulating pollutant transport and upstream salty water of a riverway with a repeated tidal flow. The device comprises an upstream flow control device, a middle water tank device and a downstream tidal flow control device, and is characterized in that the upstream flow control device comprises a water inlet pipe, a constant flow water tank and an upstream water level control water tank; the middle water tank device comprises a water tank body, a speed measuring device and a pollutant sewage inlet tank; the downstream tidal flow control device comprises a tide water level control water tank, a tide backflow stimulation water tank, a compensation or seawater salinity stimulation water tank; the upper end of the water tank body is connected with the upstream water level control water tank while the lower end thereof is connected with the tide water level control water tank; the tide water level control water tank is connected with the tide backflow stimulation water tank; the compensation or seawater salinity stimulation water tank is connected with the tide backflow stimulation water tank. The device and the method for stimulating pollutant transport and upstream salty water of riverway with the repeated tidal flow can stimulate transport and diffusion rules of the pollutants in the riverway with the repeated tidal flow (the upstream salty water rules), and can be widely applied to the simulation tests in the technical field of the water ecological environment.