Polyborate distribution in aqueous B(OH)3 solutions at 298.15K was calculated using measured pH and literature equilibrium constants.A systematic study on the structure,stability and Raman spectra of the H3BO3 hydrated clusters,[H3BO3(H2O)n,n=1-14],was probed by DFT in both gaseous and aqueous phase at B3LYP/aug-cc-pVDZ level.All of these stable configurations were described and the most stable hydrated clusters were chosen.The micro-hydration process of H3BO3 was described in detail: when n≤6,only the equatorial hydration exists in small hydration cluster; when n≥7,the axial hydration happens; when n≥12,a fully hydration structure forms with 1 axial hydration water and 9 equatorial hydration water.Transition state(TS)of H3BO3 dissociation in aqueous solution has also been located using transit-guided quasi-Newton method,indicating the axial hydration is the “powder hose” for the H3BO3 dissociation.The predicted equilibrium intra-B-O distance varies from 1.38 to 1.43 A at the present level of theory.The equatorial hydration distance ranges from 0.32 to 0.37 nm and the axial hydration distance from 0.16 to 0.18 nm with the saturated hydration number of 10.The CPMD simulation shows that only the first hydration sphere can be found,and the hydration distance is 3.65 with the hydration number about 11.8.The results reveal a good agreement with the micro-hydration from ab initio and the time-space averaged structure from X-Ray scattering.