Abstract: The surface roughness of workpiece was directly related to the tool wear in diamond cutting of optical glass. To investigate diamond cutting tool wear and its influence on the surface roughness, experiments of diamond turning with cutting distance were carried out on soda-lime glass in this work. The wear morphology of diamond tool and the material composition of flank wear area were detected, and then the corresponding surface features of soda-lime workpiece and the surface roughness were determined. Experimental results indicate that the wear on rake face was characterized by the smooth and uniform crater. The wear land on flank face extended with the increase of cutting distance and became rough gradually by micro-grooves along the cutting direction. Surface roughness, i.e. R_q, R_a and R_max of workpiece at a cutting distance of 150 m, was lower than 32, 25 and 300 nm, respectively. Once the cutting distance exceeded 150 m, the surface roughness of the workpiece increased rapidly. The main mechanisms inducing tool wear in diamond cutting of glass were mechanical wear, thermo-chemical wear and abrasive wear.