The study on the fishery of crabs was carried out from Pouk Taw, Thein Chaung, ThaPyayKone, Ywar Tan Shay, Taung Sone, Kyuak Ta Lone in Bilin Township, Mon State. The samples were collected from June, 2016 to February 2017. A total of 1 species of mud crab and 4 mangrove crabs under 3 families and 4 genera were stated, 1 species of Portunidae, 2 species of Grapsidae and 2 species of Ocypodidae were recorded in the present study. There are Scylla olivacea, Sesarma intermedian, Metaplax elegans, Uca annulipes and Tubuca. dessumidri. Scylla olivacea are economically important for local people in this study area. A total of 120 samples of each male and female mud crabs were used for investigate the carapace width and body weight relationship and length frequency distribution described in this study. In all different six stations the collected of the mud crabs (Scylla olivacea) are most abundant in October, 2016 (1680 kg) and scarce in January, 2017 (50 kg). The relationship was determined as W= 0.427 L 2.64 for male and W= 0.68 L 2.39 for female.