Abstract: Accurate measurement of the deformation on the surface of nuclear graphite is of great importance to study its mechanical properties. The boundary deformation near specimen edges cannot be accurately obtained using the subset-based digital image correlation (DIC) method, and the measured deformation field does not satisfy spatial continuity. Thus, it cannot reflect the real deformation of the nuclear graphite specimen. In order to improve the measurement accuracy and achieve the boundary deformation measurement, a new DIC method with mechanics constraints (MC-DIC) was developed in this paper. In this method, 8-node quadrilateral elements with spatial continuity were used to reconstruct the deformation field based on the trust points obtained from the subset-based DIC. The results indicate that compared with the subset-based DIC method, the MC-DIC method is more suitable for non-uniform deformation measurement, and can more accurately measure the whole field deformation of nuclear graphite specimens under loads.