The invention provides a compressing structure for a main transformer and an installation method thereof. The compressing structure comprises a coil and laminated wood symmetrically arranged at the upper part of the coil, wherein a T-shaped channel is formed in the upper surface of the laminated wood; a longitudinally arranged compressing support plate is arranged at the upper part of the laminated wood; and the compressing support plate comprises a vertical face plate and a base plate which is fixed to the bottom of the vertical face plate and is matched with the T-shaped channel. The main transformer compressing structure is simple in structure, can conveniently realize compressing fixation of the laminated wood at the upper part of the coil inside the main transformer, and is convenient to assemble and disassemble; and moreover, the integral structure stability of the main transformer can be guaranteed by using positioning convex pins.