The invention relates to a low-dielectric polymer-based wave-transparent composite material, specifically to a wave-transparent composite material prepared by using low-dielectric polyimide fiber as a reinforcement and cyanate ester resin and a filler material polyimide porous microspheres as base materials. A preparation method of the wave-transparent composite material comprises the following steps: (1) fully mixing the polyimide porous microspheres and cyanate ester resin as the base materials, and immersing the polyimide fiber fabric in the base materials to form a prepreg; and (2) executing temperature raising procedure for curing the polyimide fiber prepreg obtained in the step (1). The prepared composite material has low dielectric constant and dielectric loss and high strength and impact resistance, and can be applied in the field of radome wave-transparent materials.