As a high value lignocellulosic biomass material, beech wood has been increasingly used in advanced manufacturing. However, the machining efficiency and surface quality of beech wood are strongly influenced by cutting temperature. This study investigates the effects of cryogenic CO-assisted machining on the material removal process and surface quality of beech wood. Orthogonal cutting tests were conducted on beech wood along the grain under cryogenic and dry conditions, with cutting speed and cutting depth selected as the key variables. The results indicate that cryogenic cutting reduces the cutting force by 11%–20% and the surface roughness by 6.47%–20.31% compared with dry cutting. By inhibiting the softening of hemicellulose and lignin and reducing mechanical interlocking between wood particles and the cutting tool, cryogenic cutting significantly lowers the cutting force. In addition, cryogenic cutting strengthens the hydrogen bonding interactions among cellulose, hemicellulose, and lignin, thereby suppressing the plastic deformation of wood. The suppression of plastic deformation reduces the formation of surface burrs and pits, thereby improving surface quality. Cutting depth significantly increases both the cutting force and surface roughness, whereas increasing the cutting speed produces the opposite effect. Statistical analysis confirms that cutting depth is the dominant factor affecting both responses under cryogenic conditions. Notably, the combination of a higher cutting speed and a shallow cutting depth improves both material removal performance and surface quality. This work clarifies the mechanisms underlying the cryogenic cutting of beech wood and provides useful insights for improving the efficiency and quality of biomass processing.