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The initial strain, Trichosporon Lactis T, isolated from soil sample, having the capability of enantioselectively hydrolyzing S-isomer of racemic ibuprofen ethyl-ester into the corresponding S-ibuprofen, was implanted by 30 KeV, 1 x 10(15) ions/cm2 - 5 x 10(15) ions/cm2 low-energy N+ for the purpose of obtaining mutants with high-efficiency hydrolyzing enzyme to produce active S-ibuprofen. Under the dosage of 30 KeV, 4 x 10(15) ions/cm2, the mutation rate is the highest, with 32.9 % positive and 37.1% negative mutant, respectively. Therefore, 30 KeV, 4 x 10(15) ions/cm2 is chosen as the optimal implantation dosage. Under optimal implantation dosage, seven mutants with high-efficiency hydrolyzing enzyme are selected after N+ implantation. The genetic stability test shows that T. lactis K1, one of the seven mutants, has a stable hydrolyzing ability during consecutive five-generation. The enzyme activity of T. lactis K1 is higher with 50% than that of the initial strain after 24 h cultivation, and the highest enzyme activity of T. lactis K1 appears 6h earlier than that of the initial strain. After 24 h cultivation and succeeding 24 h incubation with ibuprofen ethyl ester, the S-ibuprofen production of T. lactis K1 is 6.96 g/L, 64.2% higher than that of T. lactis T, which only produces 4.24 g/L S-ibuprofen at the same time, the specific rotation and enantiomeric excess (ee%) of the S-ibuprofen produced by two stains, however, are the same, + 54.1 degrees and 98%, respectively.