In this report the authors investigate the influence of the construction and the dimension of toothed belt and some running conditions on the noise of toothed belt drive, and show some running noise reduction methods and their effectiveness. The running noise level varies with belt speed, belt tension and polygon-effect of the wheel, but there is no difinite tendency between noise level and number of teeth and module of the wheel. The effective methods to reduce the meshing impact sound and to keep the toothed belt drive silent are: (1) to soften the bottom lands of toothed belt or the tooth tip lands of wheel, (2) to make belt width narrow, (3) to cant the belt of tension side with an idle pulley, (4) to make the wheel noncylindrical, especially as barreled-shape.