Large area of special high liquid limit clay was formed due to the depositing in the downstream of Yellow River at Shandong province. Without the use of such clay in those plain areas in lack of filling materials, great resource waste would be caused. This paper experimentally examined the soil strength and modulus in both construction and operation periods. The high liquid limit clay in Yellow River flood area consisted of higher rounded silt particle and clay particle, which presented low volume ratio of air and high saturation degree when compacted above the optimum moisture content. Based on the filter paper tests, it was indicated that high air intake value resulted in strong water retention capacity. Through the unventilated-undrained triaxial test, the relationships between the normalized static strength, shear strength and saturation degree/volume ration of air were obtained at different compaction states. It was found that the soil had an optimum saturation ratio at 79%（volume ratio of air=8%）. The soil resilient modulus was more sensitive to the moisture contents. Although the subgrade remained safe when moisture contents increased from 20% to 23%，the compression strain increased by almost 200% due to the sharp decrease in the resilient modulus. Considering the subgrade compaction standard specified in China and Japan, the high liquid limit clay in Yellow River flood area should be compacted lower than 23% moisture content and 8% volume ratio of air，i.e.，no less than 90% compaction degree，to ensure the long-term stability of soil strength and modulus.