The guided wave testing method cannot accurately obtain the defect's normal shift at the rail web in existing research. Therefore, we investigate the normal energy distribution characteristics of hybrid high-order shear horizontal guided waves and propose a sensitive normal location method for buried defects based on guided wave relative order coefficient $\boldsymbol{G}_{\mathbf{roc}}$. As a result, we can achieve rapid and accurate location and quantification of buried defects by obtaining reflected and transmitted wave energies of different guided wave orders. The simulation and experimental results and the proposed quantification theory can be mutually verified. Results show $\boldsymbol{G}_{\mathbf{roc}}-\mathbf{based}$ defect normal shift quantification is better than commercial scanning ultrasonic body wave and eddy current detectors.