0 Introduction In recent years, the study of Y-Ba-Cu-O superconductor have made much progress. The superconducting applications are showing bright future. Generally, critical current is very lower (especially bulk sample ). The Largest J_c is only 10~3 A/cm^2. Ordinarilly, the typical critical current of Nb-Ti alloy is 10~6 A/cm^2 about 4.2 K. Hence, the level of current density have become a problem interested in by scientists. In this paper, microstrueture of Y_1 Ba_2 Cu_2 O_(7-8) superconductor is examined. The grade intersection-tunnel modal is put forward here. Some mecha-
