A high-resolution detection system was established on a beamline to accurately measure the slight broadening of crystal rocking curves, caused by cutting, clamping, adjustment, and other processes. Further, the effect of the configuration of the synchrotron radiation experiment on the rocking curve of a crystal was studied. First, the effects of different experimental configurations on the beam bandwidth and angular divergence were analyzed by producing DuMond diagrams. Using the DuMond diagram results and X-ray crystal dynamics diffraction theory, an empirical formula for the rocking curve width was derived. Moreover, a method to improve the angular resolution of the synchrotron radiation detection system was studied. A high-index surface Si (333) channel-cut crystal and a Si (775) monolithic double-crystal monochromator are used to suppress the bandwidth and angular divergence of the beam and modulate a high-resolution detection beam. Finally, a detection system was built on the X-ray test beamline at the Shanghai Synchrotron Radiation Facility. The rocking curve of the Si (111) crystal was measured by the system, and the measured result verified the empirical formula. The experimental results show that the measured value of the full width at half-maximum for the rocking curve of the Si (111) crystal is 4.79″ at 12.763 keV. This measured value is within 2% of the theoretical value of 4.70″ for dynamical diffraction, allowing small changes in the rocking curves of crystals to be detected.