Inspired by quantum theory, a novel adaptive adjustment strategy of structuring element length used for mathematical morphology is proposed, aiming at achieving better morphological extraction performance for shock response signals. First, a quantum system for vibration signals is presented using the quantum theory. On this basis, a mathematical expression of vibration signal quantum bits is given to describe the vibration signal states. Then, aiming at the local characteristics of mechanical vibration signals and correlative characteristics in 1×3 neighbor hoods, a structuring element length measurement operator using quantum probability is proposed for mechanical vibration signals. Finally, the length of the structuring element is adjusted using the length measurement operator to adaptively control structuring element length, and a better filtering effect is achieved. An example using the strategy to filter the impact fault signals of bearings is given, and the result is compared to that detected with a conventional method. The results show that the proposed method can effectively extract both global and local information.