Abstract: Mal-management of the irrigation and drainage has led to the occurrence and expansion of secondary salinization in arid and semi-arid area. Taking Weigan River Irrigation District as a case and utilizing the monitoring data of many years, the ratio of drainage to irrigation was calculated based on hydro-salinity balance principle and its influencing factors were discussed profoundly. The critical ratio of drainage to irrigation of Weigan River Irrigation area is 9.19%. Comparison results among high-yielding farm, low-yielding farm and newly reclamation farm show that dry drainage is a practical and necessary measure to dispose soil salt. Soil salt management under the condition of water-saving irrigation was discussed. Improving efficiency of farm water utilization and maintaining necessary leaching ratio is important to achieve salt balance of irrigation area for a given irrigation scale. This research provides academic and instructive meanings for sustainable development of agriculture in semi-arid or arid irrigation region.