The present study suggests an enhanced coupling non-linear control approach for both cart positioning and load swing elimination control of underactuated bridge cranes. The significant feature of the proposed method is its superior control performance as well as its strong robustness over different/uncertain cable lengths that are the major factor influencing load swing. Owing to the underactuated nature, the load swing can merely be damped out by the cart motion. Inspired by this inherent mechanism and also motivated by the desire to achieve an improved control performance, we enhance the coupling behaviour between the cart movement and the load swing by introducing a new composite signal, and on this basis, propose a non-linear control law. Lyapunov-based mathematical analysis is implemented to support the theoretical derivations. To verify its control performance, both numerical simulation and hardware experiment results are included to illustrate that the proposed method can achieve superior control results and admit strong robustness with respect to different/uncertain cable lengths and external disturbances.