The design of a novel transmission for reduction is reported in this paper. The transmission is based on the layout of triangle mechanisms, for it is intended to reduce speed. Two course of the reduction, that we term Rotating-Straight-Rotating (R-S-R), are described here, namely, first rotation movement is transformed to straight movement and then straight movement is transformed to rotating movement again though two triangle screw structure. The reducer can be applied to the purpose of the large-scale reducing speed.