The invention relates to a middle driving shift device which mainly comprises a power transfer part (A), a middle driving part (B) and an oil cylinder part (C); the middle driving part is connected with the oil cylinder part at the right to realize left-right straight shift; the power driving part is arranged at the left and is connected with a shaft of the driving part through a shaft joint; and the middle driving part comprises a gear (18) with an inner spline, which drives a spline shaft (14) and is matched with the driving spline shaft (14), and a driving body (19) driven by the gear.