Abstract: The elevated oxygen consumpt ion following exhaustive exercise, termed /excess post-exercise oxygen consumption(EPOC) can be used to assess the non-aerobic oxygen cost of exercise.To investigate the relat ionship between body weight andnon-aerobic oxygen capacity, the effect of body weight (100g) on EPOCwas study in Chinese catfish (Silurus asotus Linnaeus) at 25e using a open-flow respirometer designed by our laboratory. Resting oxygen consumption rates decreased significantly with the increase of body weight (p2/min#kg for 100 g body weight groups, respectively. The oxygen consumption was immediately increased to peak value at 2 min after exhaustive exercise and slowly decreased to a stabilized level. Peak oxygen consumption rates decreased significantly with the increase of body weight (p2/min#kg for100 g body size groups, respectively.The change of post-exercise oxygen consumption rate could be described as VO2=-a + be-ct.Where -a. could be considered as rest ing oxygen consumption,-b. as potential metabolic scope elicited by exhaustive exercise and -c. as a parameter for recovery rate of post-exercise oxygen consumption rate.The equations were VO2= 4.20+-7.-96e-0.-133t (-n= 21, R2= 0. 922, p2= 3.84+6. 68e-0.094t (n= 15, R2= 0.902, p2=3.74+ 5. 68e-0.089t (-n = 16, R2= 0. 774, p2= 3. 41 + 5.37e-0.080t(n= 7, R2= 0. 803, p 100g group.The values of-a., -b. and -c. all decreased with the increase of bodyweight, but the EPOC had an increased tendency with the increased of body weight and calculated EPOC by above equations were 59. 85, 71. 06, 63. 82 and 67. 13 mgO2, respectively.The calculated recovery time were 5. 21, 7. 37, 7. 79 and 8. 66min for post exercise oxygen consumption rate returning to 50% pre-exercise level, 22. 52, 31. 87, 33. 66 and 37. 44min for post-exercise oxygen consumption rate returning to 95% pre-exercise level and 34. 63, 48. 99, 51. 74 and 57. 56 for post-exercise oxygen consumption rate returning to 99% pre-exercise level. It suggested that non-aerobic capacity might increase while aerobic capacity decreasewith the increase of bodyweight by analyzing and comparing the parameters (a, b and c) of the mathematics model.