Underground coal separation process

Disclosed is an underground coal preparation process adopting a water medium, comprising: feeding exploited raw coal into a Φ25 mm raw coal classifying screen for screening; performing dry coal preparation on a classifying screen oversize product with a particle size greater than 25 mm and feeding a classifying screen undersize product with a particle size less than 25 mm into a special underground compact jigging machine for sorting to obtain jigging machine overflow clean coal, jigging middling coal and jigging gangue; screening and dewatering the jigging machine overflow clean coal to obtain a clean coal product, and screening and dewatering the jigging middling coal to obtain a middling coal product, sorting slime water to be sorted and generated during sorting to obtain coarse clean coal slime and coarse middling coal slime, and performing circulating water treatment on a final liquid.