Owing to the absorption and scattering of water and its impurities in underwater optical imaging, the underwater images obtained by conventional optical imaging methods have disadvantages such as low image contrast and short visible distance. In this study, a laser field synchronous scanning underwater optical imaging system is proposed. First, a 520-nm-wavelength line-structure laser is employed as the light source, and a Galvo galvanometer controls the line laser beam to scan the target plane in one dimension to form a two-dimensional illumination light field. Subsequently, the camera uses a scientific complementary metal oxide semiconductor (sCMOS) image sensor with an electronic roll-shutter to compress the instantaneous field of view of the camera into a narrow strip by reducing the exposure time. Finally, the light source is controlled to synchronously illuminate the instantaneous field of view of the camera, and the overlap volume of the light path between the camera and the light source is significantly compressed, greatly reducing the influence of water backscattering on the imaging. In this study, turbidity and distance experiments are conducted in a pool. The results of the turbidity experiment reveal that when the water turbidity is 19.6 FTU, the peak contrast improves by 4.7 times, and the peak contrast signal-to-noise ratio improves by 2.1 times. In the distance experiment, when the water attenuation coefficient is 0.2, and the imaging distance is 13 m, the peak contrast improves by 5.6 times, and the peak contrast signal-to-noise ratio improves by 2.8 times. Clear imaging is achieved at the 15-m range. This method effectively reduces the impact of backscattering on image quality, facilitating further development of underwater tasks and demonstrating high applicability in the field of underwater imaging.