The invention relates to a method for preparing high-purity cysteamine hydrochloride. The method comprises the following steps: 1, reacting carbon disulfide with sodium sulfide in a methanol aqueous solution to obtain sodium thiocarbonate; step 2, fully reacting 2-aminoethyl sulfate sodium salt or 2-chloroethylamine hydrochloride with the sodium thiocarbonate prepared in the step 1; 3, continuously adding hydrochloric acid for reaction to obtain cysteamine hydrochloride first-section mother liquor; 4, extracting the cysteamine hydrochloride mother liquor obtained in the step 3 to remove an organic phase, cooling the remaining water phase to crystallize sodium sulfate and/or sodium chloride generated in the reaction in the step 2, and filtering after crystallization to obtain filtrate whichis cysteamine hydrochloride second-stage mother liquor; 5, carrying out reduced pressure distillation on the second-stage mother liquor, cooling and crystallizing to obtain a cysteamine hydrochloridesolid; wherein the ratio of the 2-aminoethyl sulfate sodium salt to the 2-chloroethylamine hydrochloride is 1: 1. Through further optimization, the purity is further improved, and the absolute puritycan reach 98% through reference substance detection.