Abstract: The mechanical response of periodontal ligament in a clinical condition was analyzed in this paper with a nonlinear finite element method. A three-dimensional finite element model was built through the reverse engineering method with the images gained from CT scanning, and the mechanical response of dental tissue in a clinical condition was obtained with a nonlinear constitutive model of periodontal ligament. The influence of the interaction force between teeth on the mechanical response of periodontal ligament was analyzed, also did the influence of deformation of alveolar bone under a load on tooth displacements. A digital speckle experiment was conducted at last to testify the simulation result. The result shows that: the real force acted on the dental tissue is greatly influenced by the interaction force between teeth, thusly it is important indeed to use the force which is load onto the dental tissue to evaluate the dental response.