An automatic control method was described for backward motions along rectilinear path of a tractor-trailer combination (TTC) using optimal control theory. Firstly, based on linearization kinematic equation, linear quadratic regulator (LQR) was designed using optimal control. Secondly, via the desired controller, the experiments were carried out in asphalt surfaced and a non-paving way respectively. The experimental results demonstrate that the control method can be successfully used for autonomous tractor-trailer combination along rectilinear path, and the vehicle velocity has a notable influence on the offset of TTC.