Abstract: XJM-S28 flotation machine is newly developed biggest agitation-froth machine for coal flotation in China,the key parameters of this machine is decided by similarity scale-up method and the measured data of model is identically with that of designed data.The commercial application shows that the XJM-S28 flotation machine is designed reasonable,and with best separation performance,the process capacity is 800-1000 m3/h for pulp and 80-100t/h for dry material.