The production of Monascus M1 metabolites with rice and brown rice was compared. The antiproliferation effect of Monacolin K -MK- , the ethanol extracts of fermentation product of red yeast brown rice -MBR- and rice -MR- on S180 ascitic tumor cell in vitro was studied with the MTT colorimetric method. It showed that the acid form MK was presented in MBR, and the total output of MK was higher -30%- than that of MR. The content of GABA was 298mg/g in MBR, which was 21-fold higher than that in MR. While the yield of citrinin was lower in MBR. MK alone, ethanol extracts from MR and MBR were all active in inhibiting S180 ascitic tumor cell growth. In a certain range of MK concentration -3~50μg/mL-, the capacity of antiproliferation increased gradually with the increase of the concentration. When the concentration of MK was equal, the inhibition effect of MBR and MR was significantly stronger than MK alone -p<001- .