Abstract: The electrolytic separation of actinides(An) from fission products(FPs) on solid Al cathode is one of the most promising pyrochemical reprocessing processes. In this work, the electrochemical behaviour of Pu³⁺ on active Al solid cathode was studied through the transient electrochemical method. Based on the results of cyclic voltammetry(CV) and square wave voltammetry(SWV), Pu³⁺ can be reduced into alloy through a onestep threeelectrons transfer process on Al cathode, and the reaction is irreversible. The relationship between the reduction potential of the alloy formed by Pu³⁺ with Al and temperature is E^Θ,*(Pu³⁺/PuAln)(vs. Cl^-/Cl₂)=-2.944+9.84×10^-4T. Five Pu alloys(involving Pu₃Al, PuAl, PuAl₂, PuAl₃, and PuAl₄) are formed according to the results of open circuit chronopotentiometry(OCP) together with phase diagrams of Pu-Al. Furthermore, the formation Gibbs free energies of PuAl₄ at different temperature are calculated.