Abstract: The capacitor discharge spot welding on SiC_W/2024Al alloy matrix composite sheet with 0.2 mm thickness was study.The microstructures and properties of the joint were analyzed,and the temperature field and cooling rate of nugget were calculated.The results show that the joint microstructure consists of nugget zone,heat-affected zone and semi-melt zone.The cooling rate of the joint reaches to 5.25×10⁶ K/s.The microstructure of the nugget is obviously refined and the SiC-Al interfacial reaction is not found in the middle of the joint because of high cooling rate.The width of semi-melt zone is 10 to 15 μm,which divides the nugget zone and base metal.The microstructure of heat-affected zone is not obviously coarse and keeps conformation with base metal.To obtain the high quality spot-weld joint,the welding parameters are a welding voltage of 80 V,a capacitor of 3 300 μF and a electrode pressure of 18 N.