Abstract:method for As speciation analysis was improved on the basis of Tessier sequential extraction method in ecological geochemical soil samples. Experimental conditions such as the extraction method, the extraction time and the treatment method of the extraction solution were discussed and optimized. Seven fractions of As, including the water-soluble fraction, the ion-exchange fraction, the carbonate fraction, the humic acid fraction, the Fe-Mn oxide fraction, the strong organic matter fraction and the residual fraction , were obtained from soil samples by ultrasonic extraction method, and the extraction solution was then detected by atomic fluorescence spectrometry (AFS). The detection limit and the relative standard deviation（RSD）of each state for As were less than 1.0 μg/g and 10%, respectively. The improved method\ has high accuracy, and can meet the requirement of speciation analysis of ecological geochemical soil samples.