A hinge includes a hinge arm (1) and a hinge base (6) fitting with the hinge arm. A support (2) is disposed between the hinge arm (1) and the hinge base. A first end of the support is movably connected to the hinge arm, and a second end is movably disposed with the hinge base (6). A locking position (12) is disposed on the hinge arm. A connecting piece (4) is disposed in fitting with the locking position. A first end of the connecting piece is movably connected to the body of the support, and a second end is movably connected to a first end of a rocking bar (7). The body portion of the rocking bar (7) is movably connected coaxially to a second end of the support (2) and the hinge base (6). A connecting shaft (72) is disposed on a second end of the rocking bar. A first end of a spring (3) is hung to the connecting shaft, and the other end of the spring is hung to a hanging shaft (62) that is disposed fixedly with the hinge base. Because of the connecting spring, the connecting piece and the support on the key component rocking bar, by adjusting a hole position of a connecting rivet and a force of the spring, a balancing force and a buffering force can be provided for gates with different weights in a changing way, and the adaptability is good.