The invention discloses an engineering machinery gearbox and belongs to the technical field of gearboxes. According to the engineering machinery gearbox, a fixed gear (1) is installed on an input shaft I, a fixed gear (11) is installed on an output shaft VI, three fixed gears are installed on a middle shaft V, hub gears are installed on a middle shaft II, a middle shaft III and a middle shaft IV respectively, two clutches and two movable gears are installed on the middle shaft II, two clutches and three movable gears are installed on the middle shaft III, and a clutch and a movable gear are installed on the middle shaft IV. According to the engineering machinery gearbox, the six power transmission shafts and the fourteen gears constitute three forward gears and two backward gears, each forward gear is achieved by closing the two corresponding clutches and meshing the corresponding gears four times, each backward gear is achieved by closing the two corresponding clutches and meshing the corresponding gears five or three times, the structure is simple, maintenance is facilitated, and the transmission efficiency of the gearbox is improved remarkably.