A stapling head assembly, comprising: a cartridge support (1), equipped detachably with a cartridge (2) an actuating block (3) with an unlocking component (32), set movably in said cartridge (2) a cutter (5), movable at least between a first position and a second position along the longitudinal direction of said cartridge support (1), said actuating block (3) is pushed to move by said cutter (5) an lockout mechanism, said lockout mechanism comprises: an lockout block (61), said lockout block (61) is set in said cartridge support (1), and movable between a third position and a fourth position along the transversal direction of said cartridge support (1) relative to said cartridge support (1) a flexible component (62), set between said cartridge support (1) and said lockout block (61), and actuating said lockout block (61) to move from said third position to said fourth position. The stapling head assembly can effectively prevent from being fired for a second time without changing the cartridge having been fired.
