Abstract: Using the gradient hydrometeorological and surface skin temperature data observed on iron tower platform in January of 2011, the characteristic parameters of evaporation duct environment such as occurrences, duct height etc and its related factors were analyzed. The results show that the evaporation duct environment near coast of the northern South China Sea (SCS) is changeable in whole winter. The average occurrence probability and modified refractivity gradient with their evaporation ducts heights less than 10 m are more than 85% and -1.7 M units/m respectively and their average diurnal variation is noticeable. There are more than 95% evaporation duct occurring at around noon and its modified refractivity gradient is -2.0 M units/m. However the occurrence probabilities become small to 80% or so in the nighttime and its modified refractivity gradient is -1.5 M units/m. The whole winter’s variation trend of evaporation duct environment appeared to be mainly caused by the changes of wind direction. The research provided a basis for quantitative analysis and forecast of the evaporation duct in the littoral of the northern SCS.