The invention relates to a method for preparing a S-p-methylbenzyl cysteine hydrochloride, and mainly aims at solving the technical problems of prior art that (1) the use of trifluoroacetate results in high cost and strong corrosiveness and (2) water is used as reaction medium owing to the use of organic solvents. The invention has the technical proposal that: a method for the preparation of S-p-methylbenzyl cysteine hydrochloride is characterized in that the S- p-methylbenzyl cysteine hydrochloride is directly generated by using the dilute hydrochloric acid as the reaction medium and making the cysteine hydrochloride directly react with the methyl-benzenemethanol. The invention provides a method for producing the S-p-methylbenzyl cysteine hydrochloride in large scale.