Keywords: 
• the typical Luochuan loess section /
• S4 /
• grain size analysis /
• area discrepancy /
• error

Abstract: The grain size of loess and paleosol sequence is regarded as one of the most important proxies to reconstruct paleoenvironment. To obtain the reliable information of climate changes, it is necessary to measure the grain size accurately. Using Mastersize2000 Laser Grain-size Analyzer, grain size of loesspalaeosol samples taken from the typical S4 soil section of Luochuan is studied through multi-preparing processes. The results show that the error of grain size measurement originates from two kinds of aspects: measurement accuracy of the machine itself and samples pretreatment processes. On the experiment, pretreatment of samples is the primary influence factor. At the same time, it was found that credible data are not obtained only through one time measurement, but more time measurements are necessary, and the average result can be used as climate proxy. But this method may made the information of rapid climate changes lost, and made changing range of the grain size inconspicuous which is affected by smoothness of the wave crest shape.