A gram-negative bacterium isolated from soap (identified as Serratia marcescens) can produce microbial red-pigmented prodigiosin. The prodigiosin was extracted using acetone after 24h cultivation period. The results revealed that the addition of 0.5% sucrose and 0.5% glycine in cultivated medium can enhance prodigiosin production, increasing 2.12-fold and 2.15-fold, respectively. Moreover, an addition of inorganic salt KH 2 PO 4 may increase 1.17-fold prodigiosin production as compared with control.The statistical experimental design was used to optimize the medium constituents for maximal prodigiosin production by S. marcescens. The experimental results showed that the optimal medium constituents were 0.5% glycine, 0.454% peptone, 1626.3ppm KH 2 PO 4 , and 0.5% sucrose. Under this optimal composition, the predicted prodigiosin production was 2230.2mg/L, and the experimental value was 2423.4mg/L for 1 day culture in shake flasks. The microbial prodigiosin productivity was enhanced by nearly 8.42-fold (from 273.3 to 2423.39mg/L).