Abstract: The paper investigated the absorption of roxarsone(4-hydroxy-3- nitrophenylarsonic acid)and p-arsanilic acid(4-aminophenylarsonic acid)by southern and northern soils in China. The results showed that southern acidic soils with high organic matter and Fe content could absorb far more the two phenylarsonic acids than that of northern soils. Humic acid added into the northern soils could increase the absorption capacity as 3 times for p-arsanilic acid and 10 times for roxarsone, and southern soil decomposed organic matter decreased significantly its absorption capacity.Adsorption isotherms of two phenylarsonic acids by southern forest soil and farm soil fitted the Langmuir equation better, the statured adsorption capacity for roxarsone and p-arsanilic acid by southern forest soil were 1 111 and 1 250 mg·kg^-1, respectively, those by southern farm soil were 66 and 250 mg·kg^-1. Initial concentration had more effects on the absorption capacity of roxarsone.