To ensure safe operation, enhance productivity and improve operation comfort for the tractors in hill area, a dual-closed-loop-PID-based active attitude adjustment system was designed. Based on the special requirements for operation in mountainous regions, an active attitude adjustment system was designed, which included pose regulation mechanism, hydraulic actuation system and the corresponding control system. Then the system dynamic model was proposed along with the dual-closed-loop PID algorithm, which were verified numerically. Numerous experiments were conducted on a tractor system designed by Shandong Wuzheng Group. The experimental results showed that the proposed active pose regulator can achieve regaining of horizontal pose in 7.5s with a maximum angular error of 0.5° and the difference of the absolute rotation angle of both rear wheel rotary mechanism was in the range of ±1°, which satisfied the application requirement. Additionally, when the tractor system was operated at firstgear speed (1.98km/h) on slopes with relatively large variation in height, the slope angle of the tractor system can be conttrolled with in ±3°, and the absolute difference of the sway angle of the wheels on both sides were within ±5°. In conclusion, the proposed active pose regulator system design can adapt to the harsh application requirement.