For quantitative evaluation problems of the influence of the atmospheric turbulence on offshore laser communication, an approach of measurement of the atmospheric refraction structure constant is proposed based on acquisition and synchronization of 850 nm and 1550 nm band of the laser. Using real-time image processing system field programmable gate array (FPGA) and multi-core digital signal processor (DSP) architecture to realize extraction of target center position and statistics of target gray, the angle of arrival fluctuation variance and the scintillation index are obtained. The dual-band results are calculated by the classic model to obtain the atmospheric structure constant of refractive index and then the obtained results of dual-band under the same condition are compared, and the parameters of the corresponding model are revised, so that the atmospheric refractive index structure constant is calculated to be relatively stable and reliable. Experimental results show that using the improved model to calculate the atmospheric refractive index structure constant, the similarity of results is not less than 80%, and the important parameters can be used as a quantitative assessment of the influence of the atmospheric turbulence on offshore laser communication.