In order to solve the problem that the traditional way of fault diagnosis and maintenance downtime unable to apply when failures of modern mechanical and electrical system occurred, the idea of fault self-healing was put forward. Referenced to the immune principle of nature, the mapping relationship was established between fault selfhealing system and the immune system, and a fault self-healing system based on immune principle was studied. The simulation model of electro-hydraulic servo system taken as an object was established through AMESim software, and its fault self-healing was designed based on immune principle after simulation and analysis of the system fault. The simulation results show the feasibility and effectiveness of the system.