The invention relates to a horizontal well forced gas drainage method with coal bed gas subjected to staged fracturing. In order to solve the problems that hole forming performance of horizontal drilling in a coal bed is poor and buried drill accidents can happen easily and to achieve the forced gas drainage effect on tectonic soft coal, the well track of a horizontal well is controlled in mudstone or sand stone with a certain range above a coal bed top boundary, and the horizontal well is docked with a drainage vertical well at a far end. An ultra deep penetration perforating technology is used, according to the requirement for certain hole density and orientation, orientated perforating is conducted downwards on the horizontal well section in a segmented mode, a steel sleeve, a well cementation cement ring and a mudstone top plate are penetrated, and the horizontal well is communicated with a target coal layer below. Then, a clear water sand carrying fracturing technology is used, staged fracturing is conducted on the target coal bed according to the requirements for large discharge capacity, large liquid amount, high prepad fluid ratio, large sand amount and middle sand ratio, and the purpose of increasing production is achieved.