Abstract: The quasi-stepless,variable-speed mechanism presented in this paper is a variable diameter type of chain-drive,stepless variable-speed installation, a meshing stepless variable speed device. It can surmount the disadvantages of the frictional stepless variable-speed mechanisms. Its advantages are high efficiency,light weight,long life,high power transmittence, while it possess also some inherent disadvantages of the chain drive,such as variance in instantaneous speed ratio,etc,It can be used in lifting, transportation and vehicle transmissions with less demanding speed ratios.It can also be for automatic production lines. It is easy to operate and is an ideal light -weight, meshing type of near-to-stepless variable speed mechanism.