The utility model discloses a servo cylinder high temperature resistant, waterproof, dustproof, anticorrosive function has. This servo cylinder can satisfy the special abominable working condition ofsintering down and the installation condition requirement of jumbo size deviation structrual installation. Specifically do, at the long device of tailpiece of the piston rod portion's increase accent,make its from fitting the potential energy reinforce when the installation of hydro -cylinder. The hydro -cylinder is installed in the protection casing that can make things convenient for quick assembly disassembly with external displacement sensor together, makes the hydro -cylinder have the long -time radiant heat of separation, resistant instantaneous naked light high temperature, anticorrosive, waterproof, dirt -proof function characteristic. When changing external displacement sensor, the change can be realized not shutting down, control form work beyond the hydro -cylinder automatic control form is not influenced. And rotational lock has been installed additional in the design between piston rod and external displacement sensor, avoids the piston rod to assault external displacement sensor's wrench movement when rotating.