The invention discloses a water adding system of a powder mixer. The water adding system comprises the powder mixer, the water adding system of the powder mixer further comprises a water adding tank and an air compressor, a water adding pipe is connected to the water adding tank, a high-pressure air output pipe of the air compressor is provided with two high-pressure gas branches, one high-pressure gas branch is connected to the water adding tank and communicates with an inner cavity of the water adding tank, a top cover of the powder mixer is provided with a water adding nozzle which communicates with the other high-pressure gas branch and the water adding pipe at the same time and mixes introduced high-pressure gas and water flow added through the water adding pipe, the two high-pressuregas branches are correspondingly provided with gas valves, and the water adding pipe is provided with a water adding valve. According to the water adding system of the powder mixer, the atomization of the water flow is fully guaranteed, so that the effect of uniformly adding the water into powder is achieved, moreover, the water adding amount is accurately controlled, and then the advantages andeffects that the product forming quality is greatly improved, and the sintering percent of pass is high are achieved.