The preparation process of DL-thero-p-methylsulfonylphenylserine ethyl ester, using p-methylsulfonylphenylserine copper as raw material and concentrated sulfuric acid as catalyst, had been studied in this paper. After studying on the factors that influenced on the preparation, the optimal conditions were determined as follows: n(p-methylsulfonylphenylserine copper) : n(concentrated sulfuric acid) : n(ethanol)=1 : 6 : 50, the reaction temperature was 83℃, the reaction time was 10 hours，the crystallization temperature was 0℃ and the value of pH, during the process of DL-thero-p-methylsulfonylphenylserine ethyl ester precipitating from ammonia, was 7.5. The yield of DL-thero-p-methylsulfonylphenylserine ethyl ester was approximately 92% under the optimal conditions. Then the DL-thero-p-methylsulfonylphenylserine ethyl ester was recycled from liquid waste, which were produced during the esterification process and the process of DL-thero-p-methylsulfonylphenylserine ethyl ester precipitating from ammonia. After that, the yield of DL-thero-p-methylsulfonylphenylserine ethyl ester increased to approximately 98%. The products were analysed and characterized by the means of IR, 1H NMR and HPLC. And it was comfirmed that the products were highly purified DL-thero-p-methylsulfonylphenylserine ethyl ester. Chiral separation of DL-thero-p-methylsulfonylphenylserine ethyl ester, using D-tartaric acid as chiral selector,the results demonstrated that the yield of D-thero-p-methylsulfonylphenylserine ethyl ester was 93.81% under the optimal conditions as follows: n (DL-thero-p-methylsulfonylphenylserine ethyl ester) : n (D-tartaric acid) : n (methanol) = 1:1:50, DL-thero-p-methylsulfonylphenylserine ethyl ester precipitated from ammonia when the value of pH was 7.5.