In this thesis, the fresh middling coke coal from Ai Coal preparation plant used as raw material was sieved to determine the dominant grain size. +0.5 mm coal samples were used to take big float-sink test in order to determine the feasibility of re-election. -0.5mm coal samples were analyzed by laboratory cell flotation test to determine the feasibility of flotation. The results showed that re-election of the middling coke coal was feasible. Based on the above results, separation methods were suggested, +0.5 mm middling coal can be reselected by spiral separator for separation, and -0.5 mm middling coal by  conventional coal flotation after flocculation floatation .