The rock asphalt which extracted from the Buton rock asphalt(BRA), served as a natural asphalt modifier for base asphalt. The aim was to study the fatigue properties of rock asphalt modified asphalts. The evaluation indexes of fatigue performance, G*50(50% of the initial modulus) and RDR(reduced dissipated energy ratio), were discussed. Then，the time sweep tests based on rheology theory were applied in stress control mode(035, 040, 045, 050MPa) and strain control mode(20%, 25%, 30%, 35%) for modified asphalt with different content. The results show that RDR is a good evaluation index, because there is an inflection point in the curve and it is very easy and convenient to determine the fatigue life for researchers. The fatigue properties of rock asphalt modified asphalts depend on the loading mode of the test. Rock asphalt can improve the fatigue life of the base asphalt in strain control mode, if the content is smaller than 15%(mass fraction); however, rock asphalt can short the fatigue life of the modified asphalt if the content continues to increase. This is because the rock asphalt itself belongs to hard asphalt. In stress control mode, with the content of rock asphalt increasing, the fatigue life of the modified asphalt becomes longer. But the modified asphalt with the large content of rock asphalt will be sensitive to stress level.