Abstract: This paper introduced the basic theory of mimic defense technology and the Dynamic Heterogeneous Redundant architecture model, summarized the technical theoretical research of mimic defense from two aspects of overall architecture analysis and local algorithm improvement, and deeply analyzed the problems faced by the railway defense-in-depth system, and the necessity of mimic defense. Combined with the actual needs and application scenarios of railway, the paper analyzed the practical application of mimicry defense technology from three aspects: some equipment mimicry transformation, overall network architecture mimicry transformation and system mimicry transformation, which had great reference significance for improving the active defense capability of railway.