The relation between J-integral near model I crack tip in the orthotropic plate and displacement derivative is derived in
this paper. Meanwhile, the relation between stress intensity factor KI and displacement is also given in this paper. With sticking film moire interferometry method, the three-point bending beam
is tested, thus the values of J-integral and KI can be obtained from the displacement field, and then the truth of relation formula between J-integral and KI in the orthotropic composite materials is experimentally verified.