Abstract: To determine the taxonomic status of the KMR-3 strain, classification and identification were carried out. To improve the production of red pigment, the fermentation medium was optimized. With KMR-3 as the tested strain, morphology, physiological and biochemical characteristics and 16S rRNA gene sequence analysis were studied. To increase the production of red pigment, the different components (peptone, yeast extract and NaCl) and the content were optimized with LB liquid medium as a basic medium. It showed that KMR-3 strain was identified as Serratia marcescens. The optimal medium for strain producing red pigment was 5g/L tryptone, and 1% glycerol, pH5.0, temperature 28℃. Under this condition, the pigment yield was 13.4 times than those of basic medium. The culture medium not only had the characteristics of little protein using amount, but also promoted the Serratia marcescens to quickly produce a large amount of red pigment, and provided the basis for large-scale production.