Effect of activating device on the property of tap water was studied by surface tensiometer and pH meter. The results showed that the surface tension of tap water activated by the device reduced and pH value increased. The variations of surface tension and pH value are connected with flow rates. The larger flow rate, the less variation of surface tension and pH value when at the same cycle time, however, the more variation of surface tension and pH value when at the same activating time. Activated by the device, 17O NMR half width of tap water reduced from 70.79Hz at the inlet to 60.87Hz at the outlet. Reduction of surface tension were caused by hydrogen bonds in water clusters which were weakened or broken by far-infrared radiation of functional ceramic ball and galvanic cell action of copper-zinc alloy. Increment of pH value were caused by H+ in water exchanging with metal cations on surface of far-infrared ceramic balls and dissolved oxygen getting electron and forming OH-1 with the function of copper-zinc alloy.