The roof and floor of No.15 lower coal seam in Ruilong Mine is mudstone, which is mined by fully mechanized caving mining. In the process of stopping mining and removing support, it is easy to occur the phenomenon of bottom subsidence or roof leakage, which affects the normal replacement of the mine. Taking the 150202 lower outer fully mechanized caving face of the mine as the engineering background, aiming at the problem of weak mudstone roof and floor, the roof and floor reinforcement methods are proposed respectively. The roof is supported by anchor net cable + metal steel beam, and the floor is backfilled by undercover + C20 concrete. Through reinforcement, the effective control of roof and floor is realized. Combined with the optimization of the support withdrawal process, the support withdrawal speed is increased by about 30 %, which effectively alleviates the tension of mine mining replacement, and provides a reference for the support withdrawal under similar engineering geological conditions.