Organic acid is important for rock mineral corrosion and soil formation. Understanding the dissolution process of citric acid on coral sand is of great significance to the construction of island reefs. The corrosion processes of coral sand by different concentrations of citric acid at different pH values were studied. The results showed that Ca²⁺ and Mg²⁺ in coral sand were quickly dissolved in different concentration citric acid at first, and then a large amount of Ca²⁺ was fixed by citric acid to form calcium citrate precipitate. With the increase of citric acid concentration, the concentrations of Ca²⁺, Mg²⁺ and citric acid in the solution were gradually increased. The concentrations of Ca²⁺ and Mg²⁺ in the solution decreased with the increase of the initial pH of the initial citric acid solution when initial pH of citric acid solutions was lower than 7. Ca²⁺ and Mg²⁺ were mainly dissolved by the reaction of carbonate minerals with H⁺. The complex formed by Ca²⁺, Mg²⁺ and citric acid promoted the dissolution of Ca²⁺ and Mg²⁺ when the initial pH of citric acid solution was more than 7, and the concentrations of Ca²⁺ and Mg²⁺ were decreased slightly with the increase of pH. The corrosion of coral and the precipitation of calcium citrate were mainly controlled by pH. XRD and SEM analyses showed that flaky calcium citrate precipitate was formed by high concentration of citric acid reacted with coral sand, and the precipitate from the supersaturated solution was flat regular strip of calcium citrate tetrahydrate. Magnesium calcite was dissolved first during the dissolution process, followed by aragonite and finally calcite.