Objective To analyze the clinical feasibility of unilateral transforaminal lumbar interbody fusion (TLIF) for treating lumbar degenerative diseases by finite element method. Methods Based on CT scan data, three-dimensional (3D) finite element models of the normal L3-5 segments under physiological status (intact lumbar model), L4/5 with unilateral pedicle screw fixation plus interbody fusion (unilateral TLIF model) and L4/5 with bilateral pedicle screw fixation plus interbody fusion (bilateral TLIF model) were established by using Mimics, Pro/E, ANSYS software, respectively. Preload of 500 N and load of 10 N?m torque were applied on the superior surface of the L3 segment to simulate 5 physiological activities: body upright, flexion, extension, left lateral bending and right axial rotation. The deformation and stress distributions in vertebral body, vertebral discs, pedicle screw and cage under different loads were then recorded and analyzed to compare mechanical properties of the two fixation methods. Results The deformation of L3-5 segments fixed with unilateral TLIF or bilateral TLIF decreased as compared to the intact lumbar model; the stresses in cage reached the maximum in both unilateral TLIF model and bilateral TLIF model during back extension, meanwhile peak stresses on pedicle screws in unilateral TLIF were significantly higher than those on bilateral TILF model, with the peak stress of 463.39 MPa during back extension. ConclusionsUnilateral TLIF can be selected as a method for treating lumbar degenerative diseases; however, its stability was inferior to bilateral TLIF due to the higher peak stress. Therefore, less stretch exercises may be safe for patients during rehabilitation to avoid surgery failure or pedicle screw fracture.