The monacolin retard in vivo synthesis of cholestrol. This study was conducted to select the best strain of Monascus sp. for monacolin production among 21 strains. In addition, research on suitable condition for mass production was conducted. Monascus pilosus M-15 was selected as the best strain for production of monacolin. The appropriate substrate for the monacolin production seem to be as follow : glycerin 5%, glucose 2%, corn steep liquor 0.5%, sodium nitrate 0.5% and length of fermentation was at $25^{circ}C$ for 10~12days, respectively. The monacolin obtained from this organism was compared with standard monacolin using UV, IR, and GC/MS system and it was very close to the standard monacolin.