The indexes to determine the swelling potential of swelling rocks are still not unified. A series of testing results of swelling rocks of Zhangjiakou showed that: the dry saturated water absorption and the specific area of swelling rock are all correlated linearly with the content of smectite and the correlation coefficient can be reached to 87% and 96% respectively; however, content of the montmorillonite and free expansive ratio is in nonlinear correlation, which indicated that the free expansive ratio, the dry saturated water absorption and specific area can all reflect the characters of mineral components in swelling rocks. However, the liquid limit and the plasticity index were all in linear correlation with the montmorillonite content, but value of them were lower than practical ones, so they can not be suitable indexes to determine the expansibility of swelling rocks. The larger the free swelling ratio was, the larger the expensive ratio under no load was, but they have no good correlations which indicated that the properties of swelling rocks was complex, as a result it is defective tightness to determine the swelling potential only by mineral components. The swelling force and the expansive ratio under no load were also in linear correlation, which meant they can all characterize the swelling characters of swelling rocks. The lager the dry saturated water absorption was, the poorer the durability was, but the dry saturated water absorption can not reflect the disintegrative totally. Through comprehensive analysis, we took the dry saturated water absorption, coefficient of disintegrative and swelling force as the indexes to determine the swelling potential of swelling rocks.