Analyzing the working principle of traditional lens antenna can know the electric mode between metal plates is similar to that of waveguide. A new metal lens antenna is designed through changing the distance between metal plates and changing the heights of ridge. It is different from traditional metal lens antenna with concave surface structure. This metal lens antenna is composed of a plurality of rectangular metal plates with ridge on the side. This new lens antenna can adjust the aperture to make the phase distribution consistent, and therefore it can obtain high gain characteristic.