The capability of Fresnel zone plate (FZP) for light converging and splitting is calculated for normal incidence plane lights by using the Kirchhoff diffraction formula,and the results show that the capability of light converging and splitting capability is great for normal incident parallel light;the abaxial FZP′s capability of light converging and splitting exceeds the whole FZP for the same area. The ZEMAX analyses show that the abaxial FZP′s light converging and noise restraining ability is greater on condition that its area is bigger when it deviates the same distance from the FZP′s center or the distance it deviates from the FZP′s center is further when it has the same area. An optical antenna is proposed which is composed of FZP and Cassegrain telescope for atmospheric optical communication. It shows that the antenna can converge light and its noise restraining ability exceeds the paraboloid antenna.