Abstract: After the paper "the Calculation of the Force in the Belt Drive" published in Journal of Nanjing Institute of Forestry, No. 2 , 1985, this article gives some new formulas for three different forms of belt drive, which would be helpful to designing belt drives and to finding out the methods of choosing main factors of belt drives, such as the factors of contact angles of belts, diameters of pulleys, belt thicknesses, speeds of belts, etc.