For multi-component systems, harsh working environments can pose challenges in terms of accessibility for maintenance. Additionally, even after formulating a maintenance strategy, there are delays in the arrival of necessary maintenance tools and personnel. A CBM method considering maintenance preparation delay is proposed. Maintenance preparation activities for the planned maintenance and emergency maintenance are both considered. Inspection time is dynamically determined based on the maintenance preparation time and RUL prediction result. RUL for the multi-component system is predicted by combining Gamma process and Poisson process. Gamma process is used to model the internal degradation process. The homogeneous Poisson process is used to simulate the arrival process of external shocks. A threshold based on RUL prediction results is set as the maintenance standard to evaluate the maintenance effectiveness. Inspection interval, safety threshold, and maintenance threshold are optimized with the goal of minimizing the maintenance cost.