Abstract: The capacitor spot welding of 0Cr18Ni9 austenitic stainless steel sheets in 0.4 mm thickness was carried out.The microstructure and mechanical properties were investigated.The results show that the welding joint was composed of the nucleus,the heat-affected zone(HAZ) and the fusion zone between melt nucleus and HAZ.There were equiaxed austenite in the nucleus.As a result of short weld period in the capacitor discharge welding and high cooling rate of the nucleus,the rest microstrueture was similar as the matrix,the grains were dramatically refined and had a characteristic of rapid solidification.The joint with high mechanical properties,whose microhardness was 235.32 HV and the shear strength was 156.8 MPa,could be obtained as the welding voltage U was 160 V and the electrode press force F was 18 N.