Arsenic pollution has aroused widespread concern worldwide, and the removal of arsenic has immediately become a problem to be solved. The toxicity of trivalent arsenic is far higher than that of pentavalent arsenic. Arsenic mainly exists in groundwater with trivalent arsenic. The removal of arsenic in water is closely related to its hydration characteristics. However, there are few studies on the hydration characteristics around different protonated arsenite ［HmAsO3］m-3(m=2, 3), let alone the infrared spectral characteristics of ［HmAsO3］m-3(m=2, 3) hydration layer. In this paper, the B3LYP/6-311G(d, p) method was used to optimize and calculate the hydration energy of ［HmAsO3(H2O)12］m-3(m=3, 2). The type, location and intensity of interaction between water molecules and ［HmAsO3］m-3(m=3, 2) species were analyzed by using a reduced density gradient function colorimetric isosurface. The IR characteristics of ［HmAsO3(H2O)12］m-3(m=3, 2) hydrated clusters were analyzed in detail. The results show that HmAsO3 tends to be distributed on the surface of ［HmAsO3(H2O)12］m-3(m=3, 2) hydrated clusters. H3AsO3 has a lower hydration capacity than H2AsO-3. Interestingly, the first hydration layer of H3AsO3 forms a deformed six-membered ring through a hydrogen bonds, with an average bond length of 1.79 . However, the first hydration layer of H2AsO-3 forms a deformed five-membered ring through hydrogen bond, and the average bond length of hydrogen bond is also 1.79 . In the infrared spectrum, the As—OP (proton-O) stretching vibration peaks of ［H3AsO3(H2O)12］0 are 701 and 637 cm-1, which are consistent with the FTIR spectra, while the As—OP stretching vibration peaks of ［H2AsO3(H2O)12］- are 573, 562 and 449 cm-1. The As—ON (unprotonated O) stretching vibration peak is 798 cm-1. In ［H3AsO3(H2O)12］0, the independent OP—H stretching vibration peaks are 3 696 cm-1, and the OP—H stretching vibration peaks in OP—H…OW are 3 598 and 3 105 cm-1. The independent OP—H stretching vibration peak in ［H2AsO3(H2O)12］- is 3 678 cm-1, and the OP—H…OW stretching vibration peak is 3 576 cm-1. The OW—HW characteristic stretching vibration peaks of OW—HW…OW in the six-membered ring composed of the first hydration layer of H3AsO3 are 3 233 and 2 911 cm-1, and the bending vibration peak is 1 606 cm-1. When the water in the first hydration layer forms a hydrogen bond with H or OP in H3AsO3, both OW—HW stretching vibration peak and bending vibration peak shift blue. The OW—HW characteristic stretching vibration peak of OW—HW…OW in the five-member ring composed of the first hydration layer is 3 383 cm-1, and the OW—HW bending vibration peaks are 1 680, 1 674, and 1 660 cm-1. When the water in the first hydration layer of H2AsO-3 forms HW—OW…H with H of H2AsO-3, the OW—HW stretching vibration peak shifts blue, and the bending vibration peak shifts red. When the water in the first hydration layer forms a hydrogen bond with OP or ON of H2AsO-3, the OW—HW stretching vibration peak shifts red and the bending vibration peak shifts blue. Compared with the infrared characteristics of the first hydration layer of H3AsO3, the OW—HW stretching and bending vibration peaks for the first hydration layer of H2AsO-3 have a blue shift.