Daily relative humidity anomaly records of 73 stations over China have been analyzed by the method of Detrended Fluctuation Analysis (DFA for short). It is obvious that the relative humidity fluctuations take different statistical behavior from other meteorological quantities and it is found their average scaling exponent is higher than that of the temperature fluctuations. When the scaling exponents obtained from the DFA is plotted versus the standard deviation of the relative humidity fluctuations, no obvious correlation or patch behavior can be found over different areas and climate regions. So the product of the scaling exponent and the standard deviation of the same record is proposed to form a new climate region classifying index.