Abstract: Monoamine oxidases( MAOs),which are flavoprotein enzymes,are responsible for catabolism of monoamine substance in vivo. The hyperactivity and high level of monoamine oxidases will lead to some mental illness and neurodegenerative diseases. Monoamine oxidase inhibitors,as the drug for neurodegenerative diseases,were attracted much attention. Skim milk fermented by Lactobacillus rhamnosus KF7 possessed strong inhibitory activity to monoamine oxidase in vitro. To facilitate the purification of active components,the cultural conditions for Lactobacillus rhamnosus KF7 to biosynthesize monoamine oxidase inhibitors in skim milk were optimized by response surface analysis( RSA). The optimum conditions for Lactobacillus rhamnosus KF7 to biosynthesize MAOIs in skim milk was obtained as follows: inoculum concentration 3. 29%,culture temperature 34. 71℃,culture time 74. 4h. Under the optimized conditions,the estimated value and verified values for inhibitory rate were 72. 18% and 71. 98%,respectively.