Abstract: The lowfrequency internal friction Q-1 and relative shear modulus E of La₂Cu₁-xLixO_4+δ (0.02≤x≤0.15) compounds were studied by means of force fibration. For x=0.02 and 0.05, only one relaxation peak exists around 250 K and this peak is due to the hopping of O pairs. For x=0.1 and 0.15, apart from the peak P1, another peak P2 is observed at 200 K. In addition, the position of the structure phase transition revealed by shear modulus moves to lower temperature side with the Li content increasing.