Abstract: To improve the forming accuracy of thin-walled parts with smooth surface in laser metal direct manufacturing,the effect on the surface smoothness of samples is studied by different layer thicknesses.A model of layer thickness of thin-walled parts by single-trace laser cladding is proposed theoretically and studied by experimentally.The results indicate that the layer thickness can be defined as a function of the width and height of single-trace cladding layer under some conditions;when the layer thickness is equal to the value calculated,the sample can be fabricated with smooth surface.It is beneficial to choose process parameters for forming thin-walled parts in laser metal direct manufacturing.