Baker’s yeast number 6 was selected by screening. It showed good catalytic activity and enantioselectivity for asymmetric reduction of 2

5-hexanedione to produce (2

S

5

S

)-2

5-hexanediol. Gas chromatography-mass spectrometry (GC-MS) revealed that the intermediate was (

S

)-5-hydroxyhexane-2-one. Reduction of 2

5-hexanedione proceeded in a two-step reaction. The hydroxyketone was initially formed

and this intermediate was further reduced to the diol. Factors influencing the product yield and the enantiomeric excess of the reduction of 2

5-hexandione catalyzed by baker’s yeast number 6 were investigated. Higher concentration (≤100 mmol·L

-1

) of 2

5-hexandione did not influence 5-hydroxyhexane-2-one production

but 2

5-hexanediol production was inhibited by excess accumulation (30 mmol·L

-1

) of intermediate. The optimal conditions were glucose as the co-substrate at an initial glucose concentration of 20 g·L

-1

34℃

pH 7.0 and cell concentration 60 g·L

-1

(cell dry mass). Under the optimal condition and an initial substrate concentration of 30 mmol·L

-1

the yield of 2

5-hexandiol was 78.7% and the enantiomeric excess of (2

S

5

S

)-2

5-hexandiol was 94.4% for 24-h reduction.