The coelomic cavity of earthworms is filled with fluid derived from mesenchymal lining. The coelomic fluid consists of watery matrix, the plasma and a large number of coelomocytes having wide variety of functions, which plays a very important role in building innate immunity. The coelomic fluid is generally secreted by the earthworms for maintaining moisture in the body to help their physiological activities. It is generally expelled through the dorsal pores at the time of stress in response to mechanical and chemical irritation. There are various methods used for the extraction of coelomic fluid from earthworms, namely, warm water, electric shock, cold shock and heat shock methods. Out of these, cold shock method is most advantages over the other methods especially for earthworms. The coelomic fluid has many biological properties such as cytotoxic, proteolytic and anti-microbial, haemolytic, haemo-agglutinating, mitogenic activities etc. Several bioactive compounds have also been found in this coelomic fluid, exhibit a variety of biological functions.