A tractor relates to the technical field of agricultural machineries. A belt pulley of the tractor is integrated with a transmission case, the transmission case is connected with an auxiliary gear box and transmits power to the same, a speed gear selecting rod is arranged on the auxiliary gear box which is connected with a gear box, a gear shifting shaft and a gear selecting shaft are arranged on the gear box, the gear box is connected with a transfer case, a transfer selecting rod is arranged on the transfer case, one side of the transfer case is connected with a front transmission shaft connected with a front bridge, the other side of the transfer case is connected with a middle transmission shaft connected with a rear driving combination case, a rear driving operation rod is arranged on the rear driving combination case connected with a rear transmission shaft, and the rear transmission shaft is connected with a rear bridge. The tractor is simple in structure, good in reliability, high in transmission effect, stable in transmission, wide in application range, long in service life, low in cost, large in heavy load due to utilization of the above transmission system , high in working efficiency and economical utilization efficiency, flexible in turning during travelling, and convenient to utilize.