A 2D numerical study on head-on collision of detonation waves with shock waves of different strengths in the gaseous mixture of hydrogen and oxygen under equivalence-ratio state has been carried out. The NND scheme and chemical model with improved two-step reaction was used and the x-t streak schlieren diagrams and smoke foil photographics were numerically recorded to study the collision process. It was found that the transmitted detonation wave is attenuated firstly and even partially decoupled due to expansion effect. However, the collision of triple points along the detonation front can induce re-coupling which may consequently restore the detonation. In the collision process, the weak transverse waves are generated by inhomogenous combustion in the near wake of the Mach stem. The repeated collision of weak transverse waves can form new cellular structures.