To selectively separate La(III) and Ce(III) from aqueous solution, complexation-ultrafiltration and shear induced dissociation coupling with ultrafiltration were adopted with rotating disk membrane (RDM) and complexing agent polyacrylate sodium (PAAS). The effects of mass ratio of PAAS to rare earth ions (m(P)/m(RE)) and pH on rare earth rejection were investigated, and the suitable conditions of m(P)/m(RE)=4.0 and pH 5.0-7.0 were obtained. The critical shear rates of PAA-La and PAA-Ce complexes were 8.5×10⁴ and 9.0×10⁴ s^-1 at pH 5.0, respectively. Frontier orbital theory was employed to obtain the energy gap value (？E) of the complexes. The results showed that PAA-Ce complex was more stable, which was consistent with the results of the critical shear rate. The maximum selective separation coefficient (β_La/Ce) arrived at 49.3 and 16.6 under the rotating rate of 1500 r/min at pH 5.0 and 6.0, respectively. Finally, the complexation property of regenerated PAAS was studied.