Abstract: The analysis of the principle of salt mass balance in irrigation districts is the foundation for the rational drainage system design and its effective evaluation. The features for water-salt change in the irrigation districts were analyzed based on measured data. The soil salt content and the roles of the drainage system were evaluated. Moreover, the rationality of soil salt change features assessed using major ionic content instead of total ionic content was analyzed. Finally, the factors that influence soil salt content and the correlation between underground water level depth, underground water degree of mineralization and soil salt content were discussed in order to analyze and evaluate the characteristic of salt mass balance and the efficiency of the drainage system.