Abstract: The ash of clean coal product of pressure-fed 3-product H. M. cyclone is liable to fluctuate and there is high loss of clean coal in middlings. An analysis is made of the insufficiencies of the cyclone based on the data actually obtained it its field application. Practice shows that through optimization of the structure of the cyclone and its inlet and outlet as well as the structural parameters of the vortex finder and the apex angle of the 2ad-stage, the cyclone can operate with a higher efficiency and noticeably improved separation accuracy.