A series of cyclic principal stress rotation tests were carried out on intact clay to model the influence of traffic loading. The microstructure of intact clay after the cyclic loading was captured by scanning electron microscope (SEM) technology. The SEM images were analyzed according to the fractal theory by the PCAS (particle and crack analysis system) quantitative testing technology. The influence of cyclic stress ratio and frequency on the dynamic behavior of intact clay was studied according to the variation of microstructure characteristic parameters before and after cyclic loading. The test result shown that the specimens failed with less number of cycles with higher stress ratio or lower frequency. The critical failure strain tended to increase with the increasing of cyclic stress ratio, but was almost the same with different frequencies. The scale, arrangement and pattern of pores of the specimens varied regularly with the increasing of cyclic stress ratio, while the influence of frequency was irregularly. The orientation of pores was consistent with the direction of shear band in general.