Abstract: A calcuation method and calaulated results for gain and sidelobe level of a ring-focus paraboloid fed by point feeds are presented. The calculated results show that ring-focus paraboloid fed by an appropriate number of point feeds in appropriate positions has higher gain and lower sidelobe level.The characteristics depends on the number and the position of the point feeds. The characteristics is used to design a ring-focus Cassegrain antenna and it was found that it has higher gain and lower sidelobe level.