Abstract: As a reserve land resource in China, saline-sodic soil has great utilization potential; if properly developed and utilized, it will produce great benefits. Chemical methods are important for improving saline-sodic soils. In the early days, calcium-containing preparations, such as gypsum and phosphogypsum, were used to replace the exchangeable sodium adsorbed on soil colloids by adding exogenous calcium. However, saline-sodic soils are rich in calcium carbonate. Acid substances, as one of the chemical amendments, can be hydrolyzed to produce hydrogen ions. This reduces the pH of saline soil, which is conducive to dissolving calcium carbonate in soil and providing calcium sources for replacing exchangeable sodium in soil; thus reducing the addition of exogenous calcium materials and reducing the improvement cost. Based on a comprehensive analysis of domestic and foreign studies on the physical properties, saline properties, nutrient utilization, and crop yield of saline-sodic soil, this paper summarized the improvement mechanism and practice of the application of acid substances to saline-sodic soil, and forecasted its future development trend to provide a reference for saline-sodic soil management and agricultural utilization.