This book deals with electrohydraulic servo control basic theory and application technology in extreme environments. Topics covered include: the evolution of the electrohydraulic servo mechanism; the working medium of electrohydraulic servo systems; aircraft hydraulic energy; the steering engine and its sealing technology; the matching control of non-symmetrical hydraulic valves and non-symmetrical hydraulic cylinders; even and uneven under-lapping hydraulic spool valves; integrated relief valves and pressure relief valves in missiles and rockets; jet pipe servo valves; analysis methods, mathematical models and optimization design methods of electrohydraulic servo valves under extreme environments including extreme temperature, vibration, shock and centrifugal acceleration; various measures of electrohydraulic servo valves to achieve resistance to extreme environments; and ship hydraulic technology.