Objective Aiming at the clinical problem of the low matching degree with the patient’s anatomical morphology for traditional cervical fusion cage, a cervical fusion cage with the function of adjustable height and the shape matched with the vertebral body was established, and its biomechanical properties were evaluated. Methods A cervical C4-5 segment fusion model was established according to anterior cervical discectomy and fusion (ACDF), so as to simulate different motion conditions, i.e. anterior flexion, posterior extension, left/right lateral flexion, left/right rotation, and stress of the fusion cage and vertebral endplate was calculated. After three-dimensional (3D) printing of the fusion cage, an in vitro mechanical experiment was conducted to explore safety and stability of the fusion cage. ResultsThe fusion cage could keep the range of motion (ROM) of cervical vertebrae at the fusion segment with 1°-2.8° and reduce the ROM to 40%-80% of the natural segment. In the in vitro compression test, the yield load of the fusion cage was (2 721.67±209) N, which met the maximum demand of the physiological load in service state. Conclusions The designed fusion device with adjustable height shows better biomechanical properties and can reduce the selection step in operation.