Abstract:Relative humidity is one of the most important variables. So the list register w ith correct humidity observations can dispose the effect to trend of long climat e observations. From 2000 on, the man made observation which was used in past several decades was replaced by auto weather station (AWS). About 17 obs ervation stations were selected and analyzed by means of computing the annual a verage difference, standard deviation and the difference of diurnal variation. A ccording to each disadvantage of auto weather station and man made observationsystems, relative humidity was sorted to 9 species in terms of the diversity wit h temperature and relative humidity, and compared and analyzed. It is indicated that there is systemic bias between man made and auto weather observation in m ost stations. The magnitude of man made observation is usually about 3.5% larger than auto weather station. This phenomenon is more obvious in humid area. The bi as is comparatively large in humid area in the same temperature, and there is si milar result when the high temperature in the same relative humidity.