The invention relates to a dead-volume-free rocker arm three-way electromagnetic valve which comprises a valve body, a valve seat, a common port, a normally-open port, a normally-closed port, a rocker arm and a diaphragm, the valve seat covers the valve body, the rocker arm is arranged on the valve body, the diaphragm is arranged on the valve body and the rocker arm, the common port, the normally-open port and the normally-closed port are all arranged on the valve seat, and the diaphragm is arranged on the valve seat. A first flow guide wing in a curved surface body shape is arranged below the sharing opening, a fourth flow guide wing in a long strip block body shape is fixedly connected to the position, on one side of the first flow guide wing, of the diaphragm, the first flow guide wing and the fourth flow guide wing form a flow guide structure, the flow guide structure divides fluid flowing into the sharing opening into two parts, one part flows to a normally-closed opening, and the other part flows to a normally-closed opening. And the other stream flows to a normal opening. According to the invention, the basic knowledge of fluid mechanics is utilized, the structural design in the valve is innovated, and reagents originally existing in the valve, especially reagents in flowing dead angles, can be completely replaced and discharged by utilizing subsequent fluid (including reagents such as liquid or gas).