Based on the application requirements of large aperture and short focal length Fresnel lens as an antenna in the underwater wireless optical transmission system, an experimental device was built to measure the focusing performance of Fresnel lens. The 450 nm and 532 nm lasers were adopted as the test light sources, and the relationship curves between the focusing performance of Fresnel lens with an aperture of 75 mm and a focal length of 25 mm and the lens surface, laser wavelength and incident angle were obtained. The influence of incident angle of laser on the focusing spots of the 450 nm and 532 nm lasers was measured. The experimental data results show that, under the same experimental conditions, the focusing efficiency for laser passing through the serrated surface of Fresnel lens is 10%~15% higher than that through the smooth surface. In addition, the focusing efficiency of Fresnel lens for 532 nm laser is about 5.4% higher than that of 450 nm laser. With the increase of incident angle, the focusing efficiency of Fresnel lens decreases gradually, and the focusing efficiency at a 0° incident angle is 25% higher than that at ±30°. Furthermore, when the incident angle of laser is 5°, the comet aberration occurs at the focusing spot of the 450 nm laser, and when the incident angle of laser increases to 15°, the comet aberration also occurs at the focusing spot of the 532 nm laser.