Abstract: Cu/diamond composites integrate the high thermal conductivity of copper matrix with the ultrahigh hardness and superior thermal conductivity of diamond particles, exhibiting promising application prospects in key fields such as chip heat dissipation and aerospace engineering. Nevertheless, owing to the substantial discrepancies in physical and mechanical properties between diamond and copper, the surface roughness of the material is difficult to control during machining, which restricts the dimensional precision and service reliability of its engineering applications. In this paper, a systematic experimental research on the grinding surface roughness of Cu/diamond composites is carried out, and grinding tests are performed on Cu/diamond composites using diamond grinding wheels. Based on the observation of machined surface topography, the formation mechanism of surface defects on Cu/diamond composites is investigated, and the variation rules of surface roughness under different grinding depths, wheel rotational speeds and abrasive grain sizes are comparatively analyzed. The experimental results demonstrate that the typical surface defects mainly consist of step features induced by over-cutting of copper matrix, pull-out of diamond reinforcing particles, brittle spalling at particle edges and machining scratches. The surface roughness decreases with the increase of grinding depth. Moderately increasing the rotational speed of the grinding wheel can optimize the surface roughness, whereas excessively high rotational speed will deteriorate the surface quality. A smaller abrasive grain size contributes to a lower surface roughness of the workpiece. A two-stage grinding process is proposed for Cu/diamond matrix composites. It is recommended that a two-stage grinding process be applied to Cu/diamond composites. During rough grinding, a W20 diamond grinding wheel is utilized with a spindle speed of 3000 r/min and a per-pass depth of cut of 10 μm to boost the material removal rate. For finish grinding, the grinding wheel is replaced with a W5 diamond wheel while keeping the spindle speed constant, and the per-pass depth of cut is lowered to 5 μm to optimize the surface roughness of the workpiece.