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According to the structural characteristics of heavy articulated wheel tractor,a steer-by-wire system of the tractor was set up, consisted of electrical control system, angular displacement sensors, mechanical system and hydraulic steering system. The equivalent mathematical model of hydraulic steering system of the tractor was set up with nonlinear state space method by 12 parameters. Controlled by fuzzy self-tuning PID system, the articulated tractor simulation programs consisted of multi-body dynamics system and hydraulic system were developed, with help of Matlab software. The in-situ steering simulations of the tractor with the steering by wire system were carried out. Experiments on rigid road were carried out, and the results showed that the steering by wire system was suitable to the tractor operation condition when the speed was less than 13 km/h.