Abstract: The morphology, distribution and element composition of cracks in cross-section of resistance spot welding joint of the galvanized medium manganese steel were studied by optical microscope and scanning electron microscopy(SEM) with energy dispersive spectrometer system(EDS) and electron backscattered scattering detection(EBSD).The result show that 88.1% of the cracks are located at the indentation slop, and 87.5%% of the cracks are superficial cracks with a depth of less than 50 μm; zinc accumulation occurs in the cracks, and the cracks are intergranular cracks.It is inferred that the cracks belong to the liquid metal embrittlement crack, as zinc coating is melted and penetrates along the grain boundaries, intergranular crack occurs under stress.