Abstract: The fermentation conditions of Monascus sp. UV-D-9, which was a high-yield mutant obtained by complex mutagenesis, were optimized by Response Surface Methodology ( RSM) to further improve lovastatin yield.The optimum fermentation conditions were received as follows: the fermentation temperature ( X1) was 30.4 ℃, the medium volume ( X2) was134 m L, the rotation speed ( X3) was 187 r·min-1, fermentation time was 10 d and inoculation amount was 8%.The lovastatin yield of Monascus sp.UV-D-9 under the optimum conditions was ( 0.32 ± 0.014) mg·m L-1 ( n = 3) , which was increased by10.1% in comparison with the original condition.