The invention discloses an electro-hydraulic servo actuator. The electro-hydraulic servo actuator comprises an oil tank (1), an electric motor (2), a hydraulic pump (3), two filters, an overflow valve (6), a servo valve (7), a hydraulic cylinder (12), a pressure relay (15), an energy accumulator (17), a pressure gage (24), two hydraulic locks, three one-way valves, three safety valves, a two-position three-way magnetic valve (11), a two-position four-way magnetic valve (19), a three-position four-way manual directional valve (23),a manual pump (21) and a manual stop valve (16). The electro-hydraulic servo actuator adopts modular design, and the hydraulic cylinder (12) and an actuator host can be installed in a separation mode. The actuator utilizes the servo valve (7) to regulate a controlled object, and the hydraulic pump (3) and the energy accumulator (17) provide pressure oil for the servo valve (7) together. The electro-hydraulic servo actuator has the advantages that energy is saved, efficiency is high, response speed is fast, and failure self-protection function is possessed.