Present paper deals studies on Length-weight relationship of exotic fishes and their gastrosomatic index from Bansagar Colony pond from Nov. 2012 to Oct. 2013. The data of length and weight of required fishes were collected on monthly basis, using standard method given in literatures. After the collection of length-weight data of, Ctenopharyngodon idella, Cyprinus carpio (Lin.), Hypophthalmichthys molitrix (val.) Tilapia mossambica (Pet) following observations were derived. Gastrosomatic index is concerned the minimum value 2.19 for Cyprinus carpio and maximum value 6.03, while in case of silver carp Gastrosomatic index was calculated minimum 3.08 and maximum 15.82, in Tilapia minimum value was 6.91 and maximum was 14.50.