Abstract : Crabs are decapod crustaceans belonging to the infra order brachyura. They covered by exoskeleton having many pharmacological properties. This review shows about many properties of crab and chitin (exoskeleton).crab meat consist of omega 3 a polyunsaturated acid which provide protection against heart diseases. Selenium provides anti-oxidant properties. Riboflavin helps in the production of steroids and RBC’S. Skin maintenance, normal growth iron absorption and support anti- oxidant properties. copper and phosphate contained in the crab helps in the absorption , storage and metabolism of iron. Crab is used to reduce BP, psoriasis etc. Cluster of crab has application in food and medical field, agriculture, aquaculture, cosmetics and waste water and membranes. Chitin of crab is having anti-inflammatory properties and it is found that chitin is a size dependent regulator of inflammation. chitosan oligosaccharides reducing inflammation by inhibiting TNF- α in LPS stimulated inflammation. Chitin is having anti proliferative effects and it is useful for anticancer chemotherapy with decreased side effects and gradual release of drugs to cancerous cell, it can fights against several pathogenic organisms such as fungi, bacteria, yeast by its antimicrobial effect. It is observed that chitin and its derivatives are one among the powerful anti-diabetic agent , which has less side effects. Chitin can be used as anti-angiogenic agent in the formation of cancer cells . chitin also include wound healing and anti-inflammatory property .