Abstract: Three types of absorbents, ferric hydroxide, Mg-Al layered double oxide (Mg-Al-LDO) and Mg-Fe layered double oxide (Mg-Fe-LDO) were studied for their absorption on arsenite. Initial pH value of NaAsO2 solution is 9.71. After ferric hydroxide being added, the pH variation with time can be divided into 3 stages: in the first 6 minutes, pH increased from 9.71 to 10.36, which indicated that OH- from the solid phase was released into the solution; during the 7 to 40 minutes, pH changed only a little between 10.36-10.34, which indicated that the absorption of ferric hydroxide on AsO2- reached dynamic equilibrium; after 40 minutes, pH value decreased continuously to 9.72 at the 360th minute, which was caused by the condensation reaction between arsenite and the absorbent, H+ was released as a result. During the absorption of Mg-Al-LDO on arsenite, pH values increased with time continuously, this is because that Mg-Al-LDO takes anions from the solution to recover the crystal structure of its precursor, in this reaction hydroxyl is formed. It is found that Mg-Fe-LDO has double absorption effects on arsenite as shown by ferric hydroxide and Mg-Al-LDO, for that its pH-time curve is between the two absorbents. The absorption capacity of ferric hydroxide on arsenite changed a little with temperature, from 69.7mg/g at 25℃ to 73.7mg/g at 90℃. Absorption capacity of Mg-Al-LDO and Mg-Fe-LDO increased apparently when the medium was heated, from 62.4mg/g and 82.5mg/g at 25℃, to 114.9mg/g and 199.0mg/g at 90℃ respectively. Ascending absorption capacity of Mg-Al-LDO and Mg-Fe-LDO on arsenite at 90℃ is quite possibly because that the competition from carbonic anion on arsenite is suppressed by heating, which expelled dissolved CO2 from the solution.