Underwater imaging technology is a critical means to explore the ocean. With the development of underwater imaging technology, it is found that underwater turbulence is an important factor that restricts the imaging quality of optical system. Turbulence is a phenomenon of small vortices occurring at the interface due to different flow rates of each part of the medium. This physical phenomenon can directly lead to changes in the refractive index of the medium. Thus, it can change the wavefront structure of the beam, affect the modulation transfer function, and ultimately cause the degradation of the image quality at the receiving end.Most of the studies about turbulence on beam is based on refractive index and power spectrum, and the researches on turbulence is based on Nikishov's power spectrum. In this power spectrum, eddy diffusion rate is constant, does not relate to the average water temperature and the average salinity which can influence on eddy diffusion rate. Thus, the turbulence caused by the refractive index models still needs further refinement. Later, some scholars improved the refractive index fluctuation power spectrum. In this model, the average temperature and average salinity are used to characterize the vortex diffusion rate, and the refractive index fluctuation power spectrum model based on temperature and salinity is established. Compared with Nikishov's power spectrum, the power spectrum model is more complete, but the temperature variance dissipation rate and kinetic energy dissipation rate used to characterize turbulence intensity cannot be measured in the experiment, resulting in a gap between the simulation model and practical applications.In order to study the effect of underwater turbulence on the imaging quality of optical systems, we deduced the wave structure function and established an underwater optical imaging model based on the refractive index fluctuation power spectrum contained with temperature and salinity. The effects of temperature and salinity on the modulation transfer function under turbulent conditions are simulated. For verifying the reliability of the turbulence imaging model, a 3-m long underwater optical imaging experiment platform is designed and built. A water pump and water tank are used to create a turbulence region with controllable turbulence intensity. A CCD camera also plays a part of the region to image the resolution plate, thus analyzing the imaging quality. By controlling the experimental conditions, the imaging results under different temperatures and different salinity conditions are obtained. On this basis, the modulation transfer function is analyzed after the ensemble average obtained by several experiments. The results show that the modulation transfer function of the image decreases with the increase of temperature and salinity. Further studies show that the contrast of different spatial frequencies decreases linearly with the increase of salinity, and the decrease amplitude is basically the same. With the increase of temperature, the MTF basically conforms to the linear decline law, and the MTF of high-frequency components decreases faster. The experimental results show that the imaging quality under turbulent conditions is affected more by temperature than salinity, and the experimental results are consistent with the simulation results. This research has certain reference value for the design optimization and development of underwater optical systems.