The samples YBCO (123 phase) have been prepared by solid state reaction method. The influence of high power microwave on the property of high T_c YBCO superconductor has been studied by means of the measurement of superconductivity (T_c) and the SEM. The experimental results show that the transition from semiconductor to superconductor takes place at the T_co≈90K，the transition width ΔT，is widened and the grains become smaller. We think the influence results from the implused high press of high power microwave. On the one hand，the pinning cores are produced，which hinders the magnetic flux from wriggling，on the other hand. the annealing can improve the connections between grains，which benefits the improvement in the critical current density J_c.