Abstract: In the treatment of high salt wastewater emitted from the coal chemical industry in the Yellow River basin, the falling film evaporation technology was widely used, due to its advantages of high heat transfer coefficient, short material residence time and high treatment efficiency, but the evaporation process was not effective due to the difference of flow characteristics, which became one of the keys to the near zero discharge treatment of coal chemical industry. In this paper, the differences in falling film flow characteristics of 3% NaCl at different inlet velocities were studied by numerical simulation, and the axial and radial changes of the falling film flow characteristics of 3%, 5% and 7% NaCl were compared. The results showed that the effect of the change in liquid film temperature and liquid volume fraction of saline wastewater (3% NaCl) was more obvious at different inlet velocities, and the smaller the inlet velocity, the more rapid the temperature increased and the liquid volume fraction decreased. At the same inlet velocity, the difference between axial and radial temperature, axial turbulence intensity and axial and radial liquid volume of 3%, 5% and 7% NaCl was not significant, while the axial velocity and radial velocity of saline effluent with high concentration were slightly higher than other components, while the radial turbulence intensity was the opposite.