In order to explore the macroscopic mechanical properties and microscopic behavior evolution of cement-fly ash fluid solidified soil, X-ray diffraction (XRD) and scanning electron microscope (SEM) testing methods were used, combined with mechanical experiments and particle flow code (PFC) discrete element numerical simulation experiments, to study the strength characteristics of fluid solidified soil with different mix ratios under freeze-thaw action, and to analyz its mesoscopic morphology and crack evolution characteristics. The research results indicate that the flowability of fluid solidified soil is positively correlated with the dosage of cement and fly ash, and the addition of fly ash effectively reduces the wet density of fluid solidified soil. The gel material generated by the pozzolanic reaction of fly ash significantly improves the late strength and frost resistance of fluid stabilized soil. The cracks in the fluid solidified soil specimen first appear when the axial strain is about 1%, and then the number of cracks increases linearly. It tends to stabilize when the axial strain is within the range of 4% to 5%, and parallel through cracks appear on the surface of specimen.