Abstract: The connection of Al sheet and Ni sheet with both thickness of 0.1 mm was carried out by using micro-resistance spot welding, and the effect of the welding current on the microstructure, mechanical properties and electrical properties of the weld seam was studied. The reliability of the joint was tested using an accelerated power-on test. The microstructure, phase composition, electrical property and mechanical properties of the joint were studied by means of scanning electron microscopy, X-ray diffraction, four-probe detection and tensile test. The results show that With the increase of welding current from 1.20 kA-1.40 kA, the grain size of the weld joint gradually decreases, and the joint resistivity increases. Due to the large temperature difference between the weld area and the environment, the nucleation is easier and the grains are small, which intensifies the electron scattering at the grain boundary, resulting in increased resistivity. In the reliability test, with the increase of the power-on time, the grain size of the weld decreases, the joint resistivity increases, and the tensile shear force of the joint decreases. The continuous current Joule heating effect and microstructure differences of joint cause the thermal mismatch in each region of the joint, which can accelerate the initiation of microcracks and extend along the grain boundary.