Objective　To explore the motion compensation features of the lower adjacent segments after the procedure of double cervical segment fusion through biomechanic test.　Methods　Fresh specimens of human cervical spine were used in this study. Double segment fusion surgery of cervical 3-5, 4-6 or 5-7 vertebrae were simulated under the ideal non-destructive state. The effects of fusion procedure on the motion of the lower segments were analyzed under the movement conditions of flexion, extension and lateral bend. 　Results　Every kind of fusion method would effect on the motion range of the lower adjacent vertebrae at the different degree, with about 20% motion compensation between the fused and adjacent segments.　Conclusions　The motion of the lower segments will be disturbed after the double cervical segments fusion, which will increase the incorrect compensation and cause the degeneration of adjacent segment after the fusion.