This paper uses 316L stainless steel as the powder and matrix material for laser cladding. The scanning speed is 8.18mm/s, the powder feeding rate is 1.15r/min, and the laser melting is performed with a constant laser power (1002.74W) and a layer-by-layer reduction. The laser cladding experiment of single channel multilayer straight thin-walled parts is carried out under the above machining parameters. Lower power laser cladding layer by layer can effectively control the molten pool volume and improve the forming quality and precision of straight thin-walled parts. And it can be observed that the microstructure from bottom to top changes from columnar crystals to equiaxed crystals and then to columnar crystals.