A chitosanase-producing marine strain was isolated by our laboratory.Identification by rDNA-ITS sequence analysis,and it is Penicillium oxalicum.This is the first time that Penicillium oxalicum's the ability of producing chitosanase is reported.For the purpose of fermentation chitosanase in industrial,we studied oligotrophic medium components,such as source of carbon,nitrogen source,saltresistance,acidresistance and rotary speed.We explored different kinds of cheap medium for production of chitosanase.We found the soybean powder was the best,and the medium of soybean powder was as follow(g/L seawater): soybean powder 25 g,and the optimal enzyme activity was 8.5 U/mL.This medium was insufficient 5% of the cost of original.It provided direct theory and experiment foundation on industrialized production of chitosanase.