Abstract: In order to study the performance of the improved soil subgrade in the Yellow River flood retarding basin in northern Jiangsu Province, twelve series of samples of the improved soil subgrade were prepared by mixing cement, lime and fly ash with designed proportions, and then subjected to designated freezing-thawing(FT)cycles. Thereafter, the properties of compression strength and mass loss(anti-erosion)of the samples were examined. Research results showed that the compression strength and integrity of the subgrades decreased with the increase in FT cycles, and the decrease rate was obviously dependent upon the different stages during those cycles. The cement and fly ash mixture was superior to the cement and lime mixture under freeze-thaw cycles, because the soil subgrade modified with cement/lime became brittle and could be easily disintegrated. In term of individual modifier, cement can improve cohesion significantly. At an incorporation content between 2% and 7%, the cement can delay the decrease of compression strength and enhance erosion resistance of the subgrade. Lime could improve the resistance to freeze and thaw to certain extent, but may contribute to mass loss and soil erosion due to its thermal expansion nature. Similar to cement, fly ash can also delay strength decrease and maintain the integrity of soil subgrade. This study investigated the influence of different modifier on the properties of compression strength and mass loss, suggesting that the optimum mixture was 5% cement and 15% fly ash. The result can be applied to the flood retarding basin for enhancing the subgrade properties under freeze-thaw cycles.