Hydraulic prop is generally composed of piston, piston rod, cylinder block three parts. Because the support work, the column bearing capacity is large, and the drop column force is small, so the piston rod diameter is larger, often use hollow structure, in order to ensure sufficient stiffness of the piston is generally y sealing ring, copper ring guide, cylinder bottom welding. The cylinder block and the cylinder head are connected by steel wire, thread or clasp. In order to prevent the external coal seam and other stolen goods into the cylinder block, the guide sleeve should be equipped with a dustproof ring. For the single telescopic column, in order to expand the support height of the hydraulic support, can use mechanical extension rod, the head structure of the column is spherical, and the connection between the top beam or the base with pin shaft or block fixed, in order to make the column in the work by a certain adaptability. The liquid supply method of hydraulic prop consists of two ways: internal liquid supply and external liquid supply. In addition to the double telescopic column with internal liquid supply mode, the single telescopic prop is mostly external liquid supply mode, which is simple in structure, convenient in processing and maintenance.