Selective Laser Melting (SLM) technology was employed to conduct single-pass monolayer scanning experiments on cobalt tungsten carbide alloy powder under, exploring various combinations of process parameters. Analysis of the single-pass width variation under different parameters, particularly focusing on lap rate and energy density, elucidated the formation mechanism of monolayer surface morphology. The effects of laser power, scanning speed, and scanning pitch on roughness were investigated using the Super Depth of Field 3D Microscope System. Additionally, the cross-sectional morphology was examined via Scanning Electron Microscope (SEM), with elemental distribution analyzed using SEM's attached energy spectrometer. Results revealed that laser power and scanning speed predominantly influenced monolayer width through line energy density, with higher line energy density resulting in wider monolayer width. In the process of monolayer formation, the lap rate emerged as a pivotal factor in monolayer morphology, with higher lap rates correlating with lower overall surface roughness. Various process parameters affect the lap rate of the monolayer, thereby impacting its morphology. Laser power and scanning speed influence single-channel width, consequently affecting the lap rate within the same scanning spacing. Additionally, a certain combination of laser power and scanning speed directly affects the lap rate of the monolayer when the laser scanning spacing is fixed. Agglomeration of tungsten (W) elements within the monolayer cross-section was observed, potentially impacting surface quality. Optimal surface quality, with a roughness of 6.05 μm, was achieved at a laser power of 420 W, scanning speed of 500 mm·s-1, scanning spacing of 125 μm, and powder layer thickness of 40 μm.