Abstract: This article introduces something about the type of WT-22 single mastpole hydraulic expanding and contracting horsing tower which has been designed for GZY-1200 type completely hydraulic rig. In the article,the author and others mainly discuss such substance of this type of tower as its structure,working principle, the design of its main body’s structure, rising and falling mechanism, expanding and contracting mechanism,bottom supporting and locking set,tautening wipe,hydraulic system and so on.