Objective Aiming at the clinical problem of the low matching degree of traditional cervical fusion cage with the patient"s anatomical morphology, a cervical fusion cage with a highly regulated function and a shape matching with the vertebral body was used to evaluate its biomechanical properties by combining finite element method with in vitro mechanical experiment. Methods A cervical C4C5 segment fusion model was established according to anterior cervical discectomy and fusion (ACDF) to simulate different physiological postures of anterior flexion, posterior extension, left and right lateral flexion and left and right rotation, and the stress of the fusion cage and vertebral endplate was output. After 3D printing, an in vitro mechanical experiment was conducted to explore the safety of the fusion cage. Results The fusion cage can keep the range of motion of cervical vertebra at the fusion segment at 1°~2.8° and reduce it to 40%~80% of the natural segment. In the in vitro compression test, the yield load of the fusion cage is 2721.67±209N, which meets the maximum demand of physiological load in service state. Conclusions The designed height adjustable fusion device shows better biomechanical properties and can reduce the selection step in operation.