This paper explores the optimal process parameters of laser cladding nickel-based WC alloy on the surface of gray cast iron to improve the surface cladding quality of gray cast iron and avoid defects due to poor selection. Single-pass coatings were prepared by using high-power semiconductor fiber-coupled laser, and the geometric characteristics of the cladding layer were measured by using Leica optical microscope. The range results were obtained by analyzing experimental data using orthogonal range method, and the influence mechanism of the process parameters on the geometric characteristics was analyzed according to the factor effect diagram. The contour diagram of the dilution rate and the aspect ratio optimizes the range of the better process parameters according to the actual needs and finally optimizes the optimal process parameters based on the actual engineering cost. The results show that three factors have a significant impact on the geometric characteristics of the cladding layer, and laser power is the main influencing factor. The optimal process parameters are that laser power is 1 400 W, scanning speed is 5.8 mm/s, powder feeding rate is 15.5 g/min. Under the optimal process parameters, the height of the cladding layer is 1 540.5 μm, the melting width is 4 680.5 μm, the penetration depth is 88.9 μm, the dilution rate is 5.46%, and the aspect ratio is 3.04, which all meet the actual needs. This research provides a theoretical basis and reference basis for engineering practice.