Abstract: Equations of motion for two spatial flexible links robot arm system in terms of real-quasi-coordinates,which deriving from Lagrange equations of the flexible bodies in terms of quasi-coordinates,are presented.By using of the quasi-coordinates and matrix operations,the lengtly and tedious process for derivation with respect to the direction parameters are avoided,the composition of equations are compacted and it will cause the recursive formulation conveniently.Because the forms of the motion equations do not change during the description of rigid motion in various parameters,these equations of motion are of generality.