A continuous wave (CW) Nd∶YAG laser with a output power of 1 kW was used to join H62 brass and 20# low carbon steel with a thickness of 2 mm. The focused laser beam with a diameter of 0.3 mm was irradiated at the brass side of the butt joint. Thus the brass was penetratingly melted and interacted with the solid steel to form a brazing joint. The brass is penetratingly welded, and the low carbon steel is brazed. This process is called laser penetration brazing (LPB). The interfacial characterizations of the joint were investigated by metallographic microscope, scanning electron microscope (SEM) and energy dispersive X-ray spectroscope (EDS). The results show that the element diffusion and solution occur and metallurgical bonding is achieved between brass and steel. The width of the interaction layer is about 3μm. The brass weld is harder than that brass substrate and the failure occurs at the brass substrate but weld judged from the data of bursting test. The mechanic performance of H62 brass and 20# low carbon steel butt joint by laser penetration brazing can meet the demand of industrial application.