The invention discloses a washing process for coal with much ash, mud and gangue. According to the washing process, raw coal enters an air dense medium coal picker first, so that the gangue is thrown out in advance; then, the raw coal enters a three-product dense medium cyclone, so that coarse clean coal, coarse middling coal and coarse gangue are obtained; the coarse clean coal enters a medium-removing dewatering screen, so that coarse particle clean coal is obtained; the coarse gangue enters the medium-removing dewatering screen, so that the gangue is obtained; the coarse middling coal is subjected to reselection and floatation, so that fine particle clean coal, final clean coal and coal slime are obtained. A second-level flotation column is used during floatation, so that floatation efficiency and the flotation recovery rate are both high.