Abstract: Effects of thickness and density of plate on impact load and cavitation evolution in non-contact underwater explosions are investigated.A modified ghost fluid method developed recently is extended to treat nonlinear interaction between compressible flow and elastic plate.With assumption that fracture of a plate does not occur, it discloses that relatively small thickness or density of plate weakens impact of blast wave on structure.Impact load tends to result of rigid wall boundary nonlinearly with increase of thickness or density.Furthermore, smaller thickness or density causes cavitation to occur earlier and creates a larger cavitation region.It delays and weakens secondary impact on structure induced by cavitation collapse as well.