The investigations on dissociation kinetics of hydrated protonium ions,(H2O)2H+ and their deuterated species (D2O)2D+,are reported based on the harmonic and anharmonic oscillator model using the transition state theory and ab initio calculations.We find that the dissociation of (H2O)2H+ and (D2O)2D+ exhibits a distinct threshold behavior due to the existence of activation energies.Moreover,the deviation between the harmonic and anharmonic dissociation rate constants becomes larger in the high energy or temperature range,with the rate constants being unreasonably large under the harmonic oscillator model.