For solving the question about PFASS production using gangue, the best conditions for withdrawing the alkali and the silicon from the gangue during producing PFASS were obtained by using orthogonal experimental method. That is, the best acid soak conditions are: acid soak time(A) 1.5h, ratio of NaCl flux to gangue quality (B) 0.05:1, solid to liquid ratio(C) 1:10; the best alkaline leaching conditions are: alkaline leaching time 2h, concentration of the lye 5mol/L, solid to liquid ratio(C) is 1:10. PFASS, a high molecular inorganic coagulant, was prepared by gangue that is a kind of waste solid in mine. Processing conditions of the coagulant preparation were studied. The coagulant was used to treat a coal washing wastewater. The experimental results show that effluent quality is good. SS and turbidity of coal washing wastewater decrease evidently. And huge amounts of coal can be recycled.