In terms of calculation principle of graphic method and moment method, grain-size parameters of fifty-eight samples of Xiashu loess on the north bank of Yangtze River are calculated respectively, then a contrast of these two methods is made. The results indicate that the mean grain-size values derived from two methods are correlated significantly. Their relationship can be described with the equation of y=0790 3x+1512 3, the determining coefficient is 0.952 5, and the correlation coefficient is 0.976 0, which indicates that the mean grain-size values derived from two methods are equal basically and one could replace the other. The correlation equation of standard deviation is y=0.906 2x+0.109 6, the determining coefficient is 0971 2, the correlation coefficient is 0985 0, and the skewness and kurtosis are discrete and not correlated. The main reason of two different results is the different calculating principles. Graphic method reflects the characteristics of 90 percent of samples, while moment method considers the whole characteristic of grain-size distribution. The skewness is particularly on the tail of grain size distribution, and the kurtosis is particularly on the width of the apex. Because of the characteristic of paleosol′s distribution of double-apices, the differences between high-order skewness and kurtosis are obvious. By comparative study, it is found that grain-size parameters derived from moment method is more accurate and reliable to the research on xiashu loess.

graphic method; moment method; grain size parameters; Xiashu loess