Abstract: Using DC and pulse retarding field methods, we have measured the effect of in-creasing primary electron energy on the secondary emission coefficient of W-Y2O3 cermet cathode at room-temperature, and the variation of the first crossover and the maximum secondary emission coefficient (max) from room-temperature to 1500℃, respectively, The secondary emission properties are getting better as the temperature of the cathode rises. max 7 at 1400℃. The experimental results obtained in magnetrons show that this kind of cathode is good to be used in high power magnetrons at high temperature.