The invention relates to a digital image detecting flat panel transmission device which is arranged on a rack of a radiotherapy apparatus and positioned below a ray source. The digital image detecting flat panel transmission device comprises a supporting arm, a planar supporting unit and a rotating connecting piece, wherein the supporting arm is used for supporting the supporting unit, the supporting unit is used for mounting a digital image detecting flat panel and adjusting travel thereof and is a telescopic structure within the plane thereof, one end of the supporting unit is hinged to the supporting arm and positioned below the ray source, and the rotating connecting piece is connected with the supporting arm and the supporting unit and is used for driving the supporting unit to rotate to a working position, namely an unfolded state or rotate to a folded state close to the rack. The digital image detecting flat panel transmission device has the advantages that the supporting unit is the telescopic structure within the plane thereof to adjust the travel of the digital image detecting flat panel, so that ray detection travel is more precise and imaging is more precise during radiotherapy; when radiotherapy is unneeded, the supporting unit is rotated to be close to the rack, and accordingly occupied space is small, other treatment work is not hindered, working efficiency is improved, use ratio of a radiation worktable is increased and cost is saved.