Abstract: High power helical array antenna fed from planar waveguide is a new type antenna to realize the directional radiation of circularly polarized microwave, which works in C-band. The complexity and the height of the feed structure are reduced by using the planar waveguide. The structure of the basic electric probe is improved, and the coupling quantity is adjusted by controlling the central angle of the sector gap, and the reflection is eliminated by the upper and lower ridge structure. A new structure of short helical antenna is designed to optimize the axial ratio and reflection by separating the parameters, and the axial ratio of the antenna is less than 0.5 dB in the range of −7° to 7°. A 20 units linear feed array is constructed to realize equal amplitude feed by coupling energy from the planar waveguide through the electric probe structure. Finally, a helical array antenna with 20×20 units working in 4.3 GHz is simulated, and the results show that the gain of the antenna is 31.6 dB, and the aperture efficiency is 74%. The reflection is less than −16 dB within the frequency band range of 4.11−4.43 GHz and the power capacity is 3.6 GW.