To examine the change traits of chyme mass and fit to the gastric evacuation data in juvenile southern catfish(Silurus meridionalis),forty eight experimental fish［(58.45±1.66) g,(19.4±0.2) cm］were fed individually with a loach meal［(3.33±0.09) g］equivalent to 6%(5.8%±0.2%)of the catfish’s body mass,and removed from the various intervals(0,2,4,8,16,24,36,48 h)after feeding at 25 ℃.The wet and dry mass of the chyme were determined and the applicability of three mathematical models was compared by the good of fitness fitted to gastric evacuation data in juvenile southern catfish.The results of present study showed that:the wet and dry mass of remaining food in stomach as well as percentage of food residual decreased profoundly as postprandial time increased;Though three mathematical models all fitted well the gastric evacuation data,there still were several significant differences among these regression results.As mentioned above,it suggested that the best mathematical model fitted to gastric evacuation data in juvenile southern catfish was the squareroot model and its regression equations for wet mass and dry mass of the chyme mass were Y^0.5=1.889-0.051×t(R²=0.87,P<0.001)and Y^0.5=0.870-0.024×t(R²=0.86,P<0.001),respectively;The gastric evacuation rate of S.meridionalis was among the range of 0.051 g/h,and the 99% of gastric evacuation time was among the range of 36.7 h which was similar to the actual measurement values(36 h)in the present study;The juvenile southern catfish and Chinese catfish possess the similar gastric evacuation characters and the optimum mathematical model was the squareroot model.