The invention discloses an internal clamping type tension jack and a construction method thereof and relates to the technical field of tension equipment. The internal clamping type tension jack comprises a limit plate with the front end being pressed on a working anchor plate; the rear end of the limit plate is in compression joint with an oil cylinder piston through a limit plate backing ring; a tool anchor plate is arranged inside the piston; the tool anchor plate is connected with a piston rod of a piston through threads. Compared with the prior art, the internal clamping type tension jack reserves rotation space for the tool anchor plate, the tool anchor can be easily rotate to any angles with an axis of a prestressing tendon being served as a center of a circle when the tool anchor is installed, a hole of the tool anchor can be easily aligned, a reserved steel strand can penetrate the hole of the tool anchor to install the tool anchor, and angles of the tension jack are not required to rotate. The construction method is simple and the operation is simple and convenient.