Objective To develop an initial numerical model for bracketless appliance technology, and to analyze the biomechanical effects. To provide the fundamental basis to optimize the clinical application of bracketless appliance technology. Method A 3D numerical model of a dry skull was developed from sequential computed tomography (CT) scan images taken at 0.5mm intervals by using Mimics and ABAQUS software. This model consisted of three parts: a dentomaxillary model of upper anterior section, a matching bracketless appliance model, and their assembly to simulate orthodontic force stressed by bracketless appliance. The nonlinear finite element method (FEM) was used to analyze the instant biomechanical effects. As the control group, the same dentomaxillary model was loaded to simulate fixed appliance working pattern. Results The instant dentoperiodontal stress with bracketless appliance loading was much higher than that with fixed appliance working pattern by 50~500 times. With bracketless appliance loading，the tendency of tooth movement wasn’t exactly performed as planned with orthodontic teeth tending to affect each other. The canine designed to do mesiodistal translation tended to do tipping movement rather than bodily movement. Bracketless appliance itself performed stress concentration mainly in places of great deformation, but the maximal stress was less than its elastic limit of 53.1 MPa. Conclusions In this study, bracketless appliance loading performed unexpected high instant stress on dentoperiodontal tissue, with limit in controlling tooth movements. The bracketless appliance is not suggested to replace the traditional fixed appliance. This study suggested bracketless appliances should be designed more reasonable, and the material of Anglealign appliances used should be further improved, to enhance the control of orthodontic tooth movement. An ideal material for the bracketless appliance was expected to perform smaller elastic modulus, higher elastic limit and better stress relaxation.