The present invention discloses uncoupler for weight reduction treatment of excess sludge in aerobic sewage treatment process in an activated sludge method. The uncoupler is a composite which contains the components of 3, 3, 4, 5-tetrachlorosalicylanilide and refined diatomite according to the weight ratio of 1: (0.05-1.5). The uncoupler provided by the present invention can reduce the abated effect on sludge activity obviously at the same time of maintaining good sludge weight reduction performance, the positive effect is very obvious which is embodied in that the sludge weight reduction performance is stronger, and added TCS can be reduced by 20-60 percent if the same sludge weight reduction rate is achieved; and when TCS is added into the system, the removal rate of COD is basically unaffected.