[Objective] The qualitative and quantitative relations between the expansive force of weathered-sand-improved expansive soil and the effects of weathered sand content, the number of freezing-thawing cycles on the expansive force were studied. [Methods] Weathered sand was put into the expansive soil with the proportions of 0,10%,20%,30%,40%,50% and the expansive force was tested on the consolidation test apparatus in condition of freezing-thawing cycles with the times of 0,1,3,6,9,12. [Results] The expansive force of weathered-sand-improved expansive soil reduced obviously. Both the expansive force of weathered-sand-improved expansive soil and the extent of the expansive force reduces as the proportion of weathered sand increased in the same time of freezing-thawing cycles. In contrast, the two items reduced as the times of freezing-thawing cycles increased in the same proportion of mixed weathered sand. The expansive force of the weathered-sand-improved expansive soil and the natural logarithm of the number of freezing-thawing cycles showed negative linear correlation relationship in the same content of weathered sand. [Conclusion] Both of the freeze-thaw cycles and the proportion of mixed sands all affect the expansive force of expansive soil.