Abstract: To clarify the effect of welding time on the performance of WC-10Co cemented carbide/RM80 high-strength steel joints by resistance welding, butt joints were prepared in the welding time range of 10~50 ms by employing the resistance welding process. The joint strength, macro-morphology, microstructure, and elemental distribution were systematically investigated by shear test, SEM, EDS, and metallurgical microscopes. The results show that with increasing welding time, the joint shear force first increases and then decreases, reaching a peak value of 1 466.1 N at 40 ms. When the time is further extended to 50 ms, spattering becomes severe, and the strength drops back to 1 123.8 N. Both the width of heat-affected zone and the volume of the extruded nugget exhibit an initial increase followed by a decrease, attaining their maxima at 40 ms. Microstructural observations indicate that an unduly short time leads to insufficient interfacial bonding, whereas an excessive time causes metal spattering and dissolution/loss of the Co binder phase. The diffusion distances of Fe, Co, and W elements increase with welding time. The Ni coating is completely molten as the time is prolonged, yet excess energy induces porosity and cracks at 50 ms. By taking all factors into account, 40 ms is identified as the optimal welding time that provides the highest shear strength together with the fewest defects.