In this paper, we use the dispersion relation of Tokamak internal kink mode in ion kinetic regime to analyse the frequency and the growth rate of s0, the magnetic shear. We find that there is a critical shear s0c , and the resistive internal kink mode can only be excited when s0>s0c, i. e. , when q00c0 case, the growth rate of the resistive internal kink mode is several times of that obtained from the MHD regime, which is consistent with the fast crash phenomena of sawtooth. Comparison has been made of the results with experiments in the HL - 1 device for sawtooth stabilization or its period prolongation in case of hydrogen pellet refueling.