Abstract: The technical bottleneck of realizing the three-dimensional optical information transmission of space-air-ground-sea is to solve the problem of laser uplink and downlink transmission under the dynamic sea surface conditions of air-sea sea-air cross-media. This paper mainly used the blue-green laser in the seawater environment as the carrier and proposed a numerical research method for the downlink transmission of the blue-green laser through the air-sea dynamic across the medium sea surface. The effects of atmospheric sea mist, sea surface wind speed, and particle distribution in seawater on the down-transmission scattering properties of blue-green lasers were discussed in detail. The variation of blue-green laser transmittance with transmission angle under different wind speeds, and the transmittance of blue-green laser downlink transmission under different atmospheric sea mist visibility, different chlorophyll concentrations, and different bubble concentrations were numerically calculated. The results showed that when the blue-green laser is transmitted in seawater, the effect of bubbles on laser attenuation increases with the increase of wind speed and decreases with the increase of transmission depth; the transmission rate of the blue-green laser through the atmospheric sea surface and seawater gradually increases with the increase of visibility of sea mist in the atmosphere at the offshore surface. With the increase of transmission distance, the influence of chlorophyll increases gradually, and the transmittance of blue-green laser decreases. The work in this paper provides theoretical and technical support for the cross-media wireless optical transmission and communication of blue-green lasers uplink and downlink across the air-sea and sea-air.