The invention relates to a buffer overflow valve which comprises a valve body with a ladder type through hole, a screw sleeve connected to the upper end of the valve body, a valve sleeve connected tothe lower end of the valve body, a buffer valve element, a buffer piston, an adjusting rod and a spring. A first oil port and a second oil port are formed in the valve sleeve; the buffer valve elementcan be arranged in the valve sleeve in an up-and-down sliding way so as to be used for controlling the on and the off of the first oil port and the second oil port; the buffer piston is slidably matched in the valve body; a buffer cavity is formed between the buffer piston and the screw sleeve; a spring cavity is formed among the buffer piston, the valve sleeve and the buffer valve element; the adjusting rod is connected onto the screw sleeve; and the spring is arranged in the spring cavity. The buffer overflow valve is simple and reasonable in structure, low in processing and manufacturing cost, convenient to install, and good in buffer effect.