A novel experimental methodology based on nuclear magnetic resonance (NMR) is proposed to examine sensitivity damage mechanisms in clay-containing reservoirs. We successfully implemented this methodology for Nanyang tight oil reservoir. By performing experiments under conditions of different brine salinities and pH values, the degrees of potential salt and alkali sensitivity damage were determined first; thereafter, the damage mechanisms were identified by analyzing the NMR T-2 spectra and (magnetic resonance) MR images. The T-2 spectra clearly showed the quantitative exchange between small pores and big pores, and the changes in pore size at different positions in the core were visualized in the MR images obtained before the centrifugation of the core. To understand the behavior of clay size variation and clay migration in the damage process, the core was centrifuged, leaving only the clay bound water in the core, and then MR images were acquired again. The salt sensitivity damage mechanisms of clay swelling and clay migration and alkali sensitivity damage mechanism of clay dispersion and migration in Nanyang tight oil reservoir were effectively identified. Additionally, owing to the use of core-scale MR images, the sensitivity damage processes at the reservoir scale could be interpreted well.