In this study, (S)-3-hydroxy-3-phenylpropionate was prepared continuously by coupling microbial transformation and membrane separation. The effect of several factors on membrane flux, reactor capacity, and reaction conversion were investigated. A kinetic model of the continuous reduction process was also developed. The appropriate molecular weight cut-off of the ultrafiltration membrane was 30 kDa. The reactor capacity reached a maximum of 0.136/h at a biomass concentration and membrane flux of 86 g/L (dry weight/reaction volume) and 20 L/h, respectively. The (S)-3-hydroxy-3-phenylpropionate yield was 3.68 mmol/L/day after continuous reduction over seven days. The enantiometric excess of (S)-3-hydroxy-3-phenylpropionate reached above 99.5%. The kinetic constants of continuous reduction were as follows: $r_m=3.00{ imes}10^{-3}$ mol/L/h, $k_{cat}=3.49{ imes}10^{-4}$ mol/L/h, $k_1=3.09{ imes}10^{-2}$ mol/L, and $k_2=5.00{ imes}10^{-7}$ mol/L. The kinetic model was in good agreement with the experimental data obtained during continuous reduction. Compared with batch reduction, continuous reduction can significantly improve the catalytic efficiency of microbial cells and increase the reactor capacity.