Abstract: In this study, the relationship between the body length and weight was analyzed in two fish species, Aspiorhynchus laticeps （Day） and Schizothorax irregularis （Day）, which are now the endangered fish species in Weigan River of the Tarim water system. Specimens of these two native fish species were collected during the period of 2011 to 2012, and then preserved in 4% formalin. The specimens were characterized morphologically. The length-weight relationship of A. laticeps was described by the formula W=0.010L3.044 （R2=0.994） and that of S. irregularis was described by W=0.027L2784 （R2=0.910）. The results showed that both the species grew evenly. But the growth of S. irregularis was unstable. Both species were slightly slim. There were significant differences in the length-weight relationship between males and females in both above species （P〈 0.05）.