By gradually adding a low content of methyl acetoacetate into a solid medium, a new yeast strain, called MAA yeast, was separated from commercial baker's yeast. The new yeast was used for catalyzing asymmetric reduction of methyl acetoacetate in the aqueous phase, and results showed that it was more efficient than regular baker's yeast in the asymmetric reduction of methyl acetoacetate. The influence of external environment, pH, and temperature on MAA yeast was the same as on baker's yeast. The yield of methyl beta-hydroxybutanoate with the new strain was about 13% higher than with baker's yeast at 0.05 M methyl acetoacetate. Similar results were also obtained in experiments, when MAA yeast was used to catalyze other systems, such as reducing ethyl 4-chloro-3-oxobutanoate to (S)-4-chloro-3-hydroxybutanoate and reducing ethyl acetoacetate to ethyl (S)-3-hydroxybutyrate. In addition, the main product was (S)-methyl beta-hydroxybutanoate at low substrate concentration; however, (R)-methyl beta-hydroxybutanoate would be obtained when the concentration of substrate exceeded 0.4 M. The morphology of the new strain is the same as that of baker's yeast.