To measure the stress and deformation inside resin composites rapidly and dynamically, a B-scan method based on phase contrast spectral optical coherence tomography was employed to measure the out-of-plane displacement field and strain field of the resin composites with voiding defect. A bending experiment and a thermal deformation experiment were conducted for composite samples through mechanical charging and thermal loading. Then the phase difference data from experiments were unwrapped and the out-of-plane displacement field distribution and strain field distribution were obtained. The results show that the experiments descript clearly of the dynamical deformation course around the voiding defect inside composites, from which bigger displacement and strain have been observed in the stress concentration region rather than the undamaged part, and an area with the depth 1 mm below the sample surface is measured. Moreover, this method is able to measure the displacement field in a sub-micro meter level and the deformation courses of composites in dynamics, and is an effective analysis method for mechanical properties of composites.