Casing Head Assembly are installed in the lower end of wellhead equipment, connected casing string and various wellhead equipment parts,which consist of body, casing hanger and seals. Casing head used for support intermediate casing and production string load, seal off annular space between the casings, provide fitter connection for installation of the BOP, tubing head and christmas tree. Surface casing are attached to the casing head bottom flange by means of flange, and production casing are attached to the casing head by means of thread.