Abstract: It is found in engineering practice that soft soil solidified with cement is influenced by humid acid. It has been an important issue of geotechnical engineering research to identify the effect due to components of soil humic acid to soil-cement curing. This paper uses actual soft soil samples for comparative tests. Qualitative and quantitative analyses are conducted on the composition of cement stabilized soil with humic acid. The test results show the different effects of cement with humic acid for different cement contents from various places. The results shows that by Infrared spectroscopy test with the increasing of humic acid, the Cation exchange capacity of cement-soil cation increased with the increasing of cement content. For soils with cement-soil of 5%, 10%, or 20%, it is revealed form the gray relational analysist that fulvic acid makes great effort on the cement-soil unconfined compressive strength. The components of cement-soil humic acid could react with Ca2+ and Al3+ in cement-soil environment, which would produce calcium, aluminum and other key complex. They may affect the hydration reaction of cement, reduce the curing effect of cement.