The thermal protection layer of cathode plasmaelectrolytic deposition on platinum particles was prepared on Al-Si alloy.The microstructure and the heat insulation performance, fracture toughness and bending strengthof the coating were investigated by SEM, XRD, the heat insulation test device and tensile testing machine. The distribution of platinum particles in the ceramic layer is uniform, which can effectively fill the micropores of plasma discharge. The ceramic layer is mainly composed ofα-Al2O3 and t-ZrO2, and there is the formation of high temperature stable phase Zr3Y4O12in the ceramic layer. With the increase of platinum particles, the heat insulation temperature, fracture toughness and bending strength gradually increase.After thermal shock, no obvious cracks were found on the surface of the coating, which indicated that the coating had good thermal shock resistance.