The shock compaction effects on the structural and superconducting properties of high-T-c YB2C3Oy particles are investigated. YB2C3Oy particles with an average size of 960 nm were prepared by the dry-type jet mill. The lattice constants of the orthorhombic cell with a = 0.383 nm, b = 0.390 nm and c = 1.17 nm for as-shocked YB2C3Oy particles are calculated just after the shock compaction under 5.71 GPa. In the measurements of susceptibility by SQUID magnetometer, DeltaM is obtained. It is found that DeltaM(0.00232 emu/g) for as-shocked YB2C3Oy particles after annealing at 870 degreesC for 10 h is larger than DeltaM(0.00047 emu/g) for as-shocked YB2C3Oy particles, which seems to indicate the new pinning centres created around the grain boundaries during annealing. From scanning electron microscopy observations, the surface of the specimens for as-shocked YB2C3Oy has large grains of 4-15 mum in length partly with large growth-steps caused mainly by heats generated in shock compaction. Also from the section analysis of atomic force microscope image, the vertical distance of about 30-80 nm is obtained around the edge area in annealed YB2C3Oy grains.