Duloxetine, a prominent 5-hydroxytryptamine norepinephrine reuptake inhibitor, is deployed mainly in the management of adult depression, showcasing minimal side effects, swift therapeutic onset, and a robust safety profile. Ethyl (S)-3-hydroxy-3-(2-thienyl)propionate ((S)-HEES) is the crucial chiral intermediate for duloxetine production. Asymmetric synthesis of (S)-HEES using carbonyl reductase as the biocatalyst has exhibited advantages including mild reaction conditions, high catalytic efficiency and environmental friendliness. In the present study, a loop region alteration strategy was developed to screen for a carbonyl reductase for (S)-HEES synthesis and EaSDR6 from Exiguobacterium sp. s126 was identified with considerable catalytic performance and broad substrate adaptability. Site-directed mutagenesis was subsequently performed, Mut-R142A/N204A was identified with a 3.6-fold enhancement in activity relative to the wild-type EaSDR6. The mutant k