Abstract: In view of the fatigue performance of the pavement base layer under repeated loading,the full test method was used to study the variation of the fatigue life of rice husk ash cement-soil with different rice husk ash content,number of dry wet cycles,freeze-thaw cycle,and the coupling of drywet cycle and freeze-thaw cycle.The changes and mechanism of the internal microstructure of rice husk ask cement-soil were analyzed by electron microscopy scanning test.The research results indicate that the fatigue life of rice husk ash cement-soil increases with the increase of the dosage and the number of dry-wet cycles shows a trend of rising first and then falling.When the number of dry-wet cycles is 7,the fatigue characteristics are optimal,and the optimal dosage of rice husk ash is 12%.The fatigue life of rice husk cement-soil gradually decreases with the increase of freeze-thaw cycles.Under the coupling effect of dry-wet and freeze-thaw environments,the fatigue life of rice husk ash cementsoil gradually decreases with the increase of the number of action.Microscopic analysis indicates that a large amount of active substance Si O₂in rice husk ash that is formed by the reaction of cement hydration Ca（OH）₂undergoes secondary hydration reaction,generating more cementitious species C-S-H,which can inhibit the erosion of SO₄^2-in saline solution.This paper provides a solid theoretical basis for the application of rice husk ash cement-soil in practical engineering.