The mechanism of ultrasonic assisted grinding is presented. Single factor experiment method was used to conduct experiments in order to reveal the effect of different grinding parameters (including feed rate, spindle speed, grinding depth) on surface roughness and grinding force of optical glass in ultrasonic assisted grinding and conventional grinding. The experiment data wss analyzed and it shows that the surface roughness and tangential grinding force decrease while the axial grinding force increase in ultrasonic assisted grinding process than that in conventional grinding process.