A buffer device for a super-heavy-load structural parts tensile tester comprises a clamp (2), a main clamp head (3), an auxiliary clamp head (4), a displacement sensor (5), buffer bars (6), buffer retainer rings (7), loading cylinders (8), guide rails (9), force sensors (10), hydraulic buffer cylinder bases (11), hydraulic buffer cylinders (12), springs (13), a return cylinder (14), buffer cylinder pistons (15), and buffer cylinder barrels (16). The hydraulic buffer cylinders and the springs are in two-stage series connection for buffering, impact energy of the clamp heads and the clamp is largely converted into heat energy for liquid in the hydraulic cylinders, the heat is dissipated by air, and small part of the heat energy is converted into deforming potential of the springs. In addition, the springs serve as a return buffer system. Adjustment buffer time is larger than or equal to critical buffer time, so that the hydraulic buffer cylinders are imparted with fine buffering action. The buffer device is reasonable in design, stable in buffering, convenient to control, and high in reliability.