With the rapid development of the information and communication technology, intelligent operation and maintenance(OM) plays a vital role in the process of digital transformation of industrial equipment. Through the design of effective dynamic operation and maintenance strategies, enterprises can not only ensure the high availability and reliability of complex systems, but also reduce the operating costs and risks. Unlike the traditional maintenance strategy that assumes an infinite horizon, in order to design a more realistic operation and maintenance strategy in line with the reality, this study not only considers the dynamic characteristics of the preventive maintenance(PM) cost with the operating cycle under the finite time, but also establishs a PM optimization model based on a competing failure system within the finite cycle. This mode takes into account the dynamic influence of maintenance cost on the maintenance strategy for the competing failure system, and establishes a Markov decision process(MDP). Then the dynamic programming algorithm is used to determine the optimal maintenance interval and maintenance strategy with minimizing the expected total maintenance cost. Finally, a numerical example and sensitivity analysis are used to verify the effectiveness of the proposed maintenance strategy.