Tests on composite material from easy liquefaction fly ash and easy freezing silty clay according to dry weight 1:2 are conducted to investigate the dynamic properties of fly ash soils for roadbed filling. The dynamic triaxial tests are made on the two kinds of soils after freeze-thaw cycles. The variation law between the dynamic strength and the number of cycles of dynamic loading and the number of freeze-thaw cycles is obtained. The relationship curves of the dynamic stress-strain and the dynamic elastic modulus-elastic strain and the curve of the dynamic modulus and the number of freeze-thaw cycles are also given. The research shows that the dynamic properties of fly ash soils(1:2) is better than silty clay subjected to freeze-thaw cycles. After 3 cycles of freezing and thawing

its dynamic strength and dynamic modulus reach stability. It has superiority as roadbed filling.