To reduce the weight of the radome and meet the high-power application requirement, a high-power built-in curved meander-line polarization conversion radome is proposed. The radome has the curved meander-line polarization conversion plate inside the dielectric sealing cover, and through joint optimization of the arc-shaped broken wire grid unit structure and the dielectric sealing cover structure, the weight is reduced while the electric field on the metal grid is reduced, which is more conducive to engineering applications in the high-power field. In response to the application requirements of the C-band high-power linear polarization helical array antenna, a high-power polarization conversion radome with a center frequency of 4.3 GHz was optimized and loaded on the high-power helical array antenna. And the radiation characteristics and power capacity were tested. The simulation and experimental results are consistent. The radome can convert circularly polarized waves to linearly polarized waves. Its insertion loss is 0.2 dB, its axial ratio is 20 dB, and its power capacity reaches 48 MW.