The aim of this study was to establish the Length-weight relationship and Gastro-somatic index of Exotic fishes in Ranitalab 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 1.96 for Cyprinus carpio and maximum value 5.60, while in case of Grass carp it was minimum 5.08 and maximum 14.60 with silver carp Gastrosomatic index was calculated minimum 4.14 and maximum 14.93, in Tilapia minimum value was 5.59 and maximum was 17.43.