In order to study the effect of nitrogen application on the infiltration and water and salt transport in salt and alkali soil, the saline soil with salt content of 0.3%, 0.9% and 1.2% and four different nitrogen concentrations (0, 300, 600, 900 mg/L) were combined as the treatments, and one dimensional vertical soil column infiltration experiment were carried out. The results showed that:(1) Nitrogen application reduced the infiltration of saline alkali soil. Under the same nitrogen application level, the infiltration capacity of saline alkali soil decreased with the increasing of salt content, and the desalting depth also decreased. (2) With the increase of infiltration time, the soil moisture of the lower root zone was the maximum when no nitrogen was applied, and the water retention of soil was the best at this time. (3) In the saline soil with salt content of 0.3%, the amount of desalination in the soil with nitrogen application was larger than that without nitrogen application, and the nitrogen application promoted the desalination of saline alkali soil; however in saline alkali soil with salt content of 0.9% and 1.2%, the amount of desalination was higher when there was no nitrogen application, which mean that nitrogen application had an antagonistic effect on the desalination of saline alkali soil. The research results provided an effective mechanism foundation for rational nitrogen application in saline alkali soil, and provided reference for crop growth and ecological protection in salinized area.