The invention discloses a production method of calcium hydrogen citrate. Primarily, some of the citric acid solution is preliminarily mixed with tricalcium, and the rest of the citric acid solution is added in different stages and different time; thus, the acidity of the calcium hydrogen citrate reaction is kept at a proper level, the supersaturation degree of the calcium hydrogen citrate reaction can be sufficiently reduced, large-particle uniform calcium hydrogen citrate crystal can be obtained, and impurities are not embedded easily. In the invention, after the produced calcium hydrogen citrate is treated by a belt filter, the moisture and RCS are relatively low, the treatment pressure of the acidolysis section is effectively relieved, and the purity of acidolysis liquid is increased.