is an important component of the complement system, which interacts with collagen-like region of C1q and invokes many cell responses, involved in enhancing phagocytosis, promoting macrophage of microbial, inducing chemotaxis, and further enhancing the organism's immunity. In recent years, higher frequencies of disease epidemics have been reported. . Now we have successfully constructed cDNA library of ovarian tissue in , and identified PmC1qBP gene. To study the biological functions of PmC1qBP in , we compared the expression level of PmC1qBP in different tissues of female and male and development stages of ovary with semi-quantitative and real-time quantitative PCR. The results show that the expression level of PmC1qBP has significant differences between male and female in gonads, hemocytes, intestine and stomach. At the same time, the expression level of PmC1qBP is very low in nauplii and zoea larvae stage, which increases from mysis larvae stage and stabilizes during the maturation stages of ovary. The results reveal that PmC1qBP is an important functional gene during the ovary development of . The immune challenge experiment indicated that PmC1qBP is up-regulated in hepatopancreas after treated with LPS for 6 h. Penaeus monodon and might play an important function in immune regulation.