The work aims to study a selective laser melting forming process when the thickness of the first powder layer is 400 μm to solve the uneven thickness of the first powder layer during selective laser melting in additive remanufacturing. The wedge-shaped powder layer was preset on the inclined substrate, and laser scanning experiments with different laser powers were performed on the powder layer to study the effect of the wedge-shaped powder layer on the deposition. Then, powder layers of 50, 100, 200, 300, and 400 μm were preset on the horizontally placed substrates. Laser scanning experiments were performed on the powder layer to study the effects of the thickness of the powder layer on the deposition. Finally, a multi-layer deposition experiment with the first layer of 400 μm thick and the subsequent 5 layers of 50 μm each was done to study the effect of the thick powder layer on the subsequent SLM forming. Selective laser melting technology was used to repair the inclined upper surface. The increase in the thickness of the powder would cause the density of the deposited layer to become worse and the surface fluctuations increase. By increasing the laser energy density, using 300 W, 800 mm/s process parameters and laser scanning at a large layer thickness of 400 μm, the combination of the deposited layer and the substrate can be improved and the undulating contour of the upper surface of the deposited layer can be reduced. This parameter can also get a dense deposition layer when the layer thickness was small. When performing SLM scanning on the basis of the first layer with a thickness of 400 μm, the first layer deposition process should be used to deposit 5 layers as a transition zone, and the subsequent deposition can be carried out according to the normal SLM forming process. When repairing parts with SLM technology, a wedge-shaped powder layer with uneven thickness will appear on the first layer. When the thickest area of the powder layer does not exceed 400 μm, the laser power density needs to be increased for deposition. After 5 layers are deposited under high power density parameters, the normal SLM process can be used for subsequent forming.