Targeting on the problems of high energy consumption and severe abrasion for conventional ringdie briquetting machine, a new method was put forward to densify the biomass materials and also a prototype machine of epicyclic gear train structured ringdie briquetting machine with plunger roller was designed. The prototype machine can effectively compress loose materials into pellets of certain density through pressing movement of plungers of roller into the forming channels of ringdie, which altogether resemble a mating pair of gears: the plungers of roller fitting into the channels of ringdie as a pair of gears meshing with each other. For a good adjustment to diverse biomass materials, the ratio of length to diameter of forming channels can be altered. Experiments were conducted upon the prototype machine with materials (sawdust) of particle size of 1~3mm and 15% of moisture content at room temperature and 60r/min of roller rotational speed. The test results with productivity of 115kg/h, briquetting rate of 962%, bulk density of 1.05g/cm3, mechanical durability of 97.5% and an overall power consumption of 45kW〖DK〗·h/t all met the design requirements and hence the machine was proved to be satisfactorily workable，and at the same time, the energy consumption was reduced by 25.4% compared with that of the common ringdie press with similar specifications，while a 50% reduction of energy consumption was observed compared with the screw extrusion type briquetting machine. Furthermore, the wear of key components were considerably diminished and thus prolonged service life could be affirmatively expected. The biomass briquetting method can strongly support as a reference for the optimization of design and application of ringdie briquetting machine. 