Abstract: Based on evaporation duct model and electromagnetic wave propagation model, the experiments system consisted of X band microwave radar and marine atmospheric and hydrologic data acquisition and prediction system of radar maximum detection range. The observed results of the over the horizon (OTH)detection experiments done at the coast area of Yellow Sea from September to November in 2011 show that it is feasible to realize OTH detection of the shore based microwave radar using the marine evaporation duct even when radar antenna height is low. The results also show that by acquiring coastal atmospheric and hydrologic information marine target maximum detection range of shore based microwave radar can be predicted.