The invention relates to a split type reaming bit for large-diameter raising-boring used in mining machinery and an assembly method thereof. The reaming bit for large-diameter raising-boring is of a split type structure by which the bit is split and transport dimension and weight of the bit are controlled after disassembly, which solves the difficulty of transport and assembly in a narrow roadway of a coal mine, and the reaming bit has higher stability and higher reliability under combined action of great torque, tension and impact.