The invention discloses a top plate crack water guiding device and method. The top plate crack water guiding device comprises a water guiding pipe, supporting disks, gaskets, a nut and a sluice valve; the water guiding pipe extends into the internal of a drilling hole; a plurality of seamless steel pipes are connected through a steel sleeve to form into the water guiding pipe; the supporting disks, the gaskets, the nut and the sluice valve are sequentially arranged at the exposure end of the water guiding pipe; a plurality of inclined water guiding holes which are formed in a cross shape are drilled in the water guiding pipe in an interval mode; water resistance rings internally containing swelling agents are arranged on the external wall of the water guiding pipe in an interval mode; hole sealing agents are arranged between the external wall at the tail end of the water guiding pipe and the internal wall of the drilling hole; the exposure end of the water guiding pipe is connected with a flow guiding pipe which is fixed on the top plate or a channel side; a U-shaped pipe is arranged on a connection section of the flow guiding pipe and the sluice valve; the outlet end of the flow guiding pipe is connected with a water storage tank. According to the top plate crack water guiding device and method, water in the top plate cracks is guided out through a communicating vessel theory and the sealed fluid suction, a soft rock supporting system is prevented from losing efficacy due to hydration; meanwhile water yield is effectively controlled and external air is prevented from entering into the drilling hole to weather the rock formation due to the sluice valve and the U-shaped pipe; reliability, safety and persistence of the soft rock supporting system under a crack water condition are guaranteed. The top plate crack water guiding device has the advantages of being simple in structure, low in cost, easy to construct and reliable and effective.