Abstract: Reflector antenna with defocused array feed is investigated. The phased array feed moves towards the reflector and locates at the defocused area, which can enhance the beam reconfiguring ability and limited angle scanning capability. Improved projection matrix algorithm is adopted to get the excitation coefficients of the feeding phased array under phase-only control constraint. A numerical analysis is carried out in order to demonstrate the effectiveness of the approach. The patterns of the offset parabolic antenna fed by defocused feed array are effectively synthesized, including scanning and reconfigurable beams. The beam direction, beam-shape and side-lobe level requirements are met under phase-only control. The design results are verified by the simulation software GRASP.