The deviation angles of Ni-based single crystal superalloys are investigated by two techniques of rotating orientation X-ray diffraction (RO-XRD) and back-reflection Laue X-ray diffraction (BRL-XRD). The remarkable agreement between the RO-XRD and BRL-XRD methods provides strong evidence that the cutting direction has a significant effect on the deviation angle. Regardless of the deviation angle, the primary orientation angle is presented to characterize the inherent orientation changes in Ni-based single crystal superalloy, and it eliminates the effects of cutting direction. Furthermore, two pairs of diffraction peaks of the RO-XRD pattern could be developed in Ni-based single crystal superalloy, although these peaks are generally considered to take place in a bicrystal.