The equilibrium in the complex formation of some rare-earths with diglycolio acid has been investigated by the static ion-exchange method.It has been shown that under these conditions:pH=3.10,μ=0.50,C_Ln=2x10^-5 M and C_H,A=1×10^-3M(where C_H,A=total concentration of rare-earth metations,C_H,A=total concontration of the ligand diglycolic acid),complexes with compositions of 1:1,1:2,1:3 were formed.The values of formation contants calculated by the method of Fronaeus and also by that of Schubert agreed very well.