In this paper, the attenuation characteristics of 532 nm laser beam in water under different atmospheric conditions (temperature, humidity, air pressure) are investigated experimentally. Experimental results show that the attenuation coefficient of laser beam in water is significantly influenced by the atmospheric environment. The attenuation coefficient decreases with the increase of air pressure, and increases with the increase of temperature. The maximum value of attenuation coefficient of light appears in the case of high temperature and low air pressure, while the minimum value appears in the high air pressure and low temperature. The maximum attenuation coefficient of laser in water is about three times the minimum value. The mechanisms of these phenomena are discussed. These results are valuable for Brillouin lidar to achieve the remote sensing of ocean.