Abstract: Sample of soil (4.0 g) was mixed with quartz sand (2 g), Na4-EDTA (0.2 g, as ligand) and water (1.0 mL) and the mixture was evaporated to dryness under normal temperature. Acetone (4 mL), 300 g·L-1 pentafluorobenzyl bromide solution (100 μL, as derivatizing agent) and 300 g·L-1 K2CO3 solution (100 μL, as catalyst) were added to the mixture, and extraction together with derivatization was carried out ultrasonically. The supernatant (1.0 mL) was taken and evaporated to near dryness by N2-blowing. One mL of n-hexane was added and evaporated again to near dryness by N2-blowing. The volume of the n-hexane solution was made up to 1 mL, and the GC-MS analysis was carried out as prescribed. HP-5MS capillary column was used in the chromatographic separation, and negative chemical ionization was adopted in MS analysis. Linearity range for dalapon between 2.5-200 μg·kg-1 was obtained, with detection limit (3S/N) of 0.34 μg·kg-1. Recovery was tested by standard addition method using soil sample as matrix, values of recovery found were in the range of 89.1% to 106%, with values of RSD′s (n=7) ranged from 9.9% to 11%.