The invention discloses an automatic-correction-supportive hydraulic system of a rail clamp device. The hydraulic system is mainly used for passenger transportation of high-speed trains and mainly comprises a portal, a bypass oil pipe, a main oil cylinder, a main piston, a spring A, an inverted-T-shaped rail, an auxiliary oil cylinder, an auxiliary piston and a spring B. Principle of work includesthat an oil incoming pipe of the main oil cylinder pumps in hydraulic oil, a one-way valve of the oil incoming pipe is opened, a one-way valve of an oil outgoing pipe is closed, the hydraulic oil pushes the main piston to move rightwards, enters the auxiliary oil cylinder through the bypass oil pipe and pushes the auxiliary piston to move leftwards, and a clamping piece A of the main piston and aclamping piece B of the auxiliary piston clamp an upper plate of the inverted-T-shaped rail; when the hydraulic system needs to loosen the inverted-T-shaped rail, the one-way valve of the oil incoming pipe is closed, the one-way valve of the oil outgoing pipe is opened, the hydraulic oil in the main oil cylinder and the auxiliary oil cylinder flows out through the oil outgoing pipe, and the spring A and the spring B elastically extend to respectively push the main piston and the auxiliary piston to be reset.