Aiming at the problems that the chassis of crawler machine in hilly and mountainous areas is easy to roll over and the safety is poor, based on the developed structure scheme of “three-layer frame” crawler machine in hilly and mountainous areas, an interconnected omnidirectional hydraulic leveling system was designed to realize the pair-to-pair interconnection of four hydraulic cylinders in the upper frame that was horizontally levelled. The two hydraulic cylinders in the lower frame were connected in pairwise to realize longitudinal leveling. This system can make the center point of the crawler machine unchanged in horizontal leveling and longitudinal leveling. On this basis, a synchronization control strategy was proposed, which was based on the sliding mode synchronization control method based on disturbance observer. This method reduced the position error of single hydraulic cylinder and synchronous error of double hydraulic cylinder, and improved the stability of the system. The mechanical model of the crawler machine and the hydraulic model of the interconnected omnidirectional hydraulic leveling system were built in AMEsim, and the controller model was built in Simulink. The co-simulation results showed that the omnidirectional leveling system based on sliding mode synchronous position control was superior to the traditional PID control. In omnidirectional leveling, the 20° transverse leveling time can be reduced by 1.6s, the 25° longitudinal leveling time can be reduced by 1.8s, the average rising time was shortened by 21.8%, the average adjustment time was shortened by 35.5%, and the synchronous position control error was kept within ±6×10－4m. On this basis, the real machine test of the solid prototype of the “three-layer frame” crawler in hilly and mountainous areas was carried out. The average error of the tilt angle of the omnidirectional levelling body was 2.55%, and the average error of the hydraulic cylinder synchronization was 8.2%. The test results verified the feasibility and superiority of the designed omnidirectional levelling system of the crawler.