It is signality for the Yangtse River estuary fine sand filling the highway subgrade which accounting for the lacking of filler and protecting along the line environment. Experiment results indicate that the sand has high strength, low compressibility, and good water stability. But the fine sand has some characteristics as grain uniformity, badness gradation, single structure, and the fine grain, and the fine sand filling subgrade is built on the soft soil foundation with high water table, so it is hidden troubles for the fine sand filling subgrade extending and application whether it can liquefy under the tempestuous earthquake load. The paper establish the liquefaction condition, carry through the liquefaction experiments and analysis the subgrade liquefaction risk relying on the Chong Ming connection engineering of Changjiang tunnel and bridge engineering. The analysis results indicate that the yangtse river estrary fine sand cannot liquefy with 7 class earthquake load, and it has no liequefaction conditions. So the subgrade has low liquefaction risk, and can be widely application.