Compared to soil foundations, rock foundations have greater resistance and rigidity due to their rocky nature, and therefore they show the necessary load-bearing capacity against many incoming loads; however, factors such as rock mass fragmentation, discontinuities, severe weathering, karst cavities, faults, etc. reduce their load-bearing capacity. Kharg Island is one of the most important oil export terminals in Iran, where huge crude oil storage tanks with different capacities have been built. These tanks require a suitable foundation that has both sufficient load-bearing capacity and can limit settlement. In this study, various methods for determining load-bearing capacity are examined, including the use of regulations, experimental methods, analytical methods, and numerical methods. In the following, the load-bearing capacity of the rock foundations of crude oil storage tanks located on Kharg Island is determined by different methods. In this regard, the geological resistance index has been used to investigate discontinuities and weak structural factors. The results of surveys and studies show that discontinuities have a great impact on the bearing capacity of rock foundations. The bearing capacity and settlement of the foundations of Khark Island are within the permissible limits and are suitable for the construction of crude oil storage tanks.