The distribution state and occurrence form of impurities of rice husk ash were analyzed and identified by SEM/EDS and XRD. The reaction kinetics for the leaching phosphorus have been studied to determine the effect of process parameters, such as stirring speeds, temperatures, HCl concentrations, particle sizes, ultrasound powers and frequencies. The kinetic data fit a new transformation of shrinking core model. The apparent activation energy is 81.21 kJ/mol. And the reaction orders with reference to HCl concentrations, particle sizes, ultrasound powers and frequencies are determined to be 2.54, -0.59, 1.55 and -0.92, respectively. The semi-empirical equation is as follows: 1/3ln (1 - x) + [(1 - x)(-1/3) -1] 9.25 x 10(10) (C-HCl)(2.54) (d(0))-(0.59) (P-0)(1.55) (f(0))(-0.92) e(-81210/RT)t