The invention discloses a control device for an automatic shifting system of a high-power wheeled tractor, and relates to agricultural machinery. The control device is formed by a hydraulic actuating element, a circuit controlling element, an information obtaining element and an information processing element. A controller compares obtained information with set values and gives instructions after logical judgment, operation and processing. The instructions are respectively transmitted to a magnetic valve combination valve block through signal lines. The magnetic valve combination valve block supplies oil to a hydraulic actuating oil cylinder according to the instructions, so that the purposes of automatic shifting and automatic speed changing are achieved. Meanwhile, the controller further transmits all types of information of gears, rotating speeds and switch positions to a display. In this way, the speed ratio range of the gears is broadened, the density of the gears is enhanced, and fuel economy and comprehensive usage performance of the tractor are improved. Furthermore, a driver is free from onerous shifting operation and can focus more on operation of agricultural implements arranged on the tractor, working intensity is relieved, and production efficiency is improved.