Abstract: Stability constants of MO2Ac+ complex(M——U, Np, Pu: Ac——acetate) andthe rate constants of the reduction of Np(Ⅵ) by some organic compounds have been determined by potentiometry with the ion-selective electrode sensitive to hexavalent actinyl cations. Comparison is made between the results of this work and those obtained by other methods from literature. The feasibility to use this electrode in the thermodynamics study of complexation and kinetics study of redox of actinide elements is evaluated.