Ocean atmospheric duct is an important atmospheric environmental factor that can affect reconnaissance warning equipment and civil navigation support equipment.In this paper,a new technique of laser detection of atmospheric duct is introduced,the propagation characteristics of multi-wavelength laser in ocean atmosphere,refractive index structure constant of optical wave band and the mechanism model of multi-wavelength laser detecting atmospheric duct are analyzed.A lot of experiments have been carried out in Sanya and other places by using self-developed lidar,the humidity and the temperature of the atmosphere with different height were measured simultaneity when the return back signal of laser radar was collected.The vertical profile of the temperature and humidity was measured,and then the vertical profile of atmospheric refractivity was calculated.The space distribution and the temporal distribution of the refractive index structure constant were analyzed.It came to the conclusion that the vertical profile of the extinction coefficient had some clear relativity with atmospheric duct,this approved that detecting the atmospheric duct,and especially evaporation duct with laser method was probable.