The invention discloses a mechanical energy-absorbing type vehicle-mounted fuel tank in the automobile field. A left end piston and a right end piston which are sealed and slidably connected with the inner surface are arranged inside a fuel tank body, the right middle of the right end piston is fixedly connected with the left end of a right push rod, and the right end of the right push rod is fixedly connected with a right push rod base; the right middle of the left end piston is fixedly connected with the right end of a left push rod, and the left end of the left push rod is fixedly connected with a left push rod base; a left end spring is connected between a left cover and the left end piston, and a right end spring is connected between a right cover and the right end piston; and an active lever is arranged on the right side of the right push rod base, the upper end of the active lever faces to the right push rod base, the lower end of the active lever is connected with the right end of the horizontal section of an L-shaped force transferring rod, the upper end of the vertical section of the force transferring rod is fixedly connected with the left push rod base, when the shaking kinetic energy of oil plants is beyond the storage energy of the left end spring and the right end spring, the right push rod base strikes the upper end of the active rod, and the vessel volume for containing the oil plants is increased, so that the oil plants are in a rebalanced state.