The laser cladding layers on the 27SiMn steel surface are obtained by the preset powder feeding method, and the heat treatment to these cladding layers is also conducted. The microstructures, phase structures, tensile properties, fracture morphologies and microhardness specimens before and after heat treatment are investigated, and the better heat treatment process parameters are obtained. The results show that the heat treatment process can refine the grain size of cladding layers, which makes microstructures denser. The heat treatment process can improve the plasticity and toughness, which enhances the tensile strength and reduces the microhardness of materials. Under the optimal heat treatment process, the grains of specimens are refined and homogeneous, and the tensile property is superior.