The encapsulation test of 0.1 mm thick SUS304 stainless steel with BNi-2 as the intermediate layer was carried out by using resistance spot brazing technology. The influence of technological parameters on the microstructure and mechanical properties of resistance spot brazing joint was analyzed, the element distribution and phase composition in the joint area were determined, and the air tightness of the joint was verified. The results show that the resistance spot brazing joint is composed of the brazing zone, the thermomechanical affected zone and the base material; With the increase of welding current and electrode pressure, the thickness of the brazing zone decreases and the dynamic recrystallization degree of the thermomechanical affected zone increases; The high cooling rate inhibits the element diffusion between the brazing joint and the base metal, the phases of the brazing joint are nickel based solid solution and dispersively distributed fine Cr,2,B and Ni,3,B particles, the maximum shear resistance of the joint is 118.3 N; The maximum load pressure of the package element reaches 0.53 MPa, which indicates that the resistance spot brazing joint of ultra-thin austenitic stainless steel has excellent air tightness.