Roxarsone (ROX) and p-arsanilic acid (ASA) are widely used as feed additives to increase the weight of animals and are excreted in animal wastes, and the use of these animal wastes as organic fertilizers in agriculture soils will cause the pollution of arsenic in the soils. The biotransformation of roxarsone and p-arsanilic acid in agriculture soils determine their ecological risks. This study was conducted to determine ROX, ASA and their metabolites (arsenate (As(V)), arenite (As(III)), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA)) in soils by HPLC-ICP-MS/MS. Arsenic species were well separated by malonic acid within a short retention time of 9.2 min. The detection limits obtained by ICP-MS using helium collision mode and ICP-MS/MS using oxygen reaction mode were comparable. ICP-MS/MS provided a low detection limit for As(V), DMA, MMA, ASA and ROX (0.85 μg L^-1, 1.59 μg L^-1, 0.93 μg L^-1, 0.94 μg L^-1, 1.03 μg L^-1 and 1.15 μg L^-1) and excellent recoveries (93.8-105.8%). The extraction of arsenic from soils by phosphate was assisted by microwave, which provided a good extraction efficiencies for As(V), DMA, MMA, ASA and ROX (41.7%, 103.9%, 89.9%, 120.4%, 70.7%, and 84.9%). This study provided a robust and convenient analytical method for the investigation of ROX, ASA and their metabolites in soils.