Carassobarbus loteus fish, one of the Barbus species and native to southwestern Iran, have been identified in the domestic water in the rivers and wetlands of Khuzestan Province. This study was performed characteristic reproductive biology of Carassobarbus luteus in Karun River. Monthly catches from February 2012 to April 2013 at three stations in Aqili desert- of Shushtar from the Khuzestan Province. 385 samples of Carassobarbus luteus were collected from the study area. In this study, length frequency of fish entire 161.57±23.89 mm and the weight frequency 63.8±35.46 gr. The highest and lowest levels of gonadal index for the month of February (10.629±5.638) and December (0.986±0.560), respectively. In this study was identified 183 males and 180 females and 22 Carassobarbus loteus undetected in Karun River. Average oocyte diameter in sexual stages was II, III, IV and V, 13.818, 15.091, 16.265 and 16.2 mm, respectively. Maximum diameter of fish eggs were observed in February (18.52 mm) and minimum diameter of oocytes in December (13.88 mm). Mean absolute fecundity of Carassobarbus luteus were calculated 5754.59±7 and the average relative fecundity of fishes 53.30±1.03. According to this research has been done upstream spawning season because of differences with other species Barbus can be geographic location length and weight of the fish. Also this species have two peaks of spawning in October and February, so the possibility of being asynchronous spawn.