The invention discloses a wheat harvester with a hydraulic transmission device. The left end of a discharging barrel is connected with a grain warehouse of a harvester body through a soft pipe, and arotary drum at the lower side is hinged with a hydraulic cylinder, and the telescopic rod of the hydraulic cylinder is hinged with the left side of the lower end of the discharging cylinder, and the connecting point of the telescopic rod and the discharging cylinder is located on the left side of supporting rods. A control switch is mounted on the discharging cylinder, and a hydraulic pump is electrically connected to the control switch. The hydraulic pump is connected to the hydraulic cylinder through a liquid guide pipe. A control method of the wheat harvester is as follows: S1, discharging;S2, lifting; and S3, stretching. According to the invention, through work of the control switch and the hydraulic cylinder, the discharging cylinder rotates around the supporting rods, so that the discharging position can be adjusted left and right to prevent wheat from piling and spilling out in one place; and the rotary drum is rotatably connected with the supporting rods, so that a dischargingpipe can be rotated back and forth to change the position of a discharging port. At the same time, a grip can be pulled, a telescopic cylinder can be pulled out, so that the length is changed, and use is more flexible.