The frequency of dipole relaxation of liquid crystal (LC) layer at LC- solid interface, f(r), is shown to be in full correlation with the polar anchoring energy W-p; the increase of Wp is accompanied with the decrease off, This correlation is established by the use of the aligning polyimide layers treated with different methods. The anchoring energy increases and the relaxation frequency decreases in the following sequence of processes: rubbing-photoalignment-plasma beam alignment. The correlation between W-p and f(r), is an evidence of strong contribution of dipole-to-dipole interaction at the LC-substrate interface to polar anchoring of LC. Based on this correlation new method of polar anchoring measurement can be developed.