In order to address the challenges posed by low linear tracking accuracy, slow on-line speed and poor anti-disturbance rejection ability in unmanned tractor-trailer agricultural vehicles operating in unstructured environments, a straight-line path tracking control method based on fuzzy fast power sliding mode control was designed. Firstly, a straight-line path tracking error model was developed for agricultural tractor-trailer vehicles, grounded in the vehicle’s kinematic model and the reference path. A straight-line path tracking method based on fast power sliding mode theory and fuzzy parameter adjustments was proposed, which solved the sliding mode controller chattering problem and also improved the on-line speed. Rigorous Lyapunov stability analysis was presented to affirm the stability of the closed-loop system. The designed control method ensured that the tractor-trailer effectively tracked the reference path, while the articulation angle converged to zero at the same time.The effectiveness and superiority of the proposed control method were evaluated through Simulink simulations and real vehicle tests. Field experiments revealed that when employing this control method, the maximum path tracking lateral errors for the tractor and trailer were 0.11m and 0.12m, respectively, with tracking error variance values of 0.0013m2 and 0.0015m2. Compared with the traditional sliding mode controller designed based on constant reaching law, the online time was improved approximately by 58%, and the maximum tracking error was reduced roughly by 66%. The designed method can effectively improve the stability and speed of the tractor-trailer path tracking.