The effect of inclusion shape on the mode I stress intensity factor of the matrix crack interaction with a rigid inclusion was studied experimentally using digital gradient sensing (DGS) method. First, the noncontact optical measurement system of DGS was built up, and the specimens with different shapes of inclusion ahead of matrix crack were performed using transparent epoxy resin. Then, the angular deflection contour at the crack tip with different shapes of inclusions was obtained, and the stress intensity factors were extracted from the stress gradient filed based on least square fitting. Finally, a numerical simulation was conducted on the same problem using ABAQUS, and the stress intensity factors computed from FEM were compared with the experimental results. The results show that the stress intensity factors extracted from the stress gradient filed are agreed well with the numerical and theoretical results.