The ZnO based glass was added to calcined K0.5Na0.5NbO3 by ball milling for 20h. The addition of 1wt.% ZnO- based glass exhibited the following piezoelectric properties (kp=36%, Qm=236, e33T/e0=464). By increasing the amount of glass powder ~5wt.%, kp was decreased to 24%. However, Qm and e33T/e0 were observed slightly decreasing. Besides, the moisture-resistance of ZnO-based glass added K0.5Na0.5NbO3 was enhanced considerably as compared to that of K0.5Na0.5NbO3.