Equipment along the railway has different degradation paths and reliability in different environments. It is of great significance to study the reliability and maintenance strategy of equipment in dynamic environment to ensure the safety of train operation. In this paper, a method of equipment reliability modeling and periodic maintenance decision-making in dynamic environment is proposed. A reliability model considering the degradation and impact of environmental changes and considering the characteristics of the equipment is established. A new concept of maintenance cycle is defined, and a decision model of equipment periodic maintenance is established. Finally, through numerical simulation, it is concluded that under severe environment, the maintenance time is shortened by 29508h and 31639h respectively, and the maintenance cost is increased by 41.4% and 28.2% respectively. Furthermore, the change trend and adjustment scheme of the strategy under different operating environments are analyzed, which verifies the correctness and effectiveness of the model in this paper.