In order to solve the problem of the thickness and uniformity of the light emitting diode (LED) lens coupler for the existing lighting fiber bundle, a new type of Fresnel lens coupler according to the Fresnel theory and the total reflection principle is designed. The Fresnel rotating surface and the free-form surface total reflection rotation surface are used to shape the light beam emitted by the LED Lambert light source to obtain a flattened light beam, which is then coupled to the fiber bundle for uniform illumination. Using 1 W 3535 white LED as the light source, TracePro software is used to simulate the Fresnel lens coupler model. The results show that when the maximum diameter of the Fresnel lens is 14.9 mm, the thickness is 7.8 mm and the output beam divergence angle is 60°, a uniform light field with diameter of 10 mm and luminance uniformity of 92% is obtained on a receiving screen with a coupling distance of 2 mm.