Abstract Continuous polishing (CP) using a pitch lap plays a vital role in finishing large flat optical workpiece. The effects of key mechanical parameters in CP can be characterized by the contact pressure and friction force at the workpiece/lap interface. In this study, a novel on-line interfacial contact pressure and friction force wireless measurement system is developed for the practical CP process. These mechanical factors varying with polishing time are measured in experiments and its effect on material removal is theoretically analyzed. A liquid bridge model is proposed to explain the negative contact pressure at slurry channel edge and the enhanced contact pressure at the abrasive slurry lubrication condition. Experimental results reveal the material removal coefficient is linear to time average COF under given polishing conditions and there exists significant non-uniformity in material removal coefficient along the workpiece radial direction.