In this paper, we propose to enhance the transmission of EM waves through fiber-reinforced polymers (FRPs) by modifying the local field distributions using the metamaterial inclusions. Due to the higher permittivity of FRPs relative to the air, the transmission of the s-polarized waves decreases drastically with the incidence angle θi. By doping metallic strips into an FRP plate, the magnetic vectors in the plate are tilted vertically under large incidence angles, and hence, the refracted angle in the plate is increased. This is equivalent to reduce the effective permittivity of the FRP, which enables significant transmission enhancement, especially under large incidence angles. A Ku-band prototype was designed, fabricated, and measured. Both simulated and measured results verify that the metamaterial doping can achieve transmission enhancement in an ultra-wide incidence angle range θ _i ∈ [0, 80°]. This paper provides an effective route to the design of transparent radomes for base stations, aircraft, and so on.