Qualitative and quantitative relationships among unconfined compressive strength of expansive soil improved by weathered sand, weathered sand content and freeze-thaw cycle were researched. Expansive soil samples were improved by weathered sand with different blending ratios (0, 10%, 20%, 30%, 40%, 50%) and were put in universal testing machine to test the unconfined compressive strength after different cycles (0, 1, 3, 6, 9, 12) of freezing and thawing. Test results showed that with the increasing of weathered sand ratio, the unconfined compressive strength of expansive soil improved by weathered sand first increased and then decreased at the same cycles of freeze-thaw. When sand ratio was 10%, the unconfined compressive strength reached the maximum. With the increasing of freeze-thaw cycles, the unconfined compressive strength decreased in the presence of the same sand ratio, and the magnitude of the decrease also reduced with the increasing of freeze-thaw cycles. After regression analysis of test data, the mathematical model between unconfined compressive strength and freeze-thaw cycle was established. These two variables showed a natural logarithmic relationship, and this natural logarithm between unconfined compressive strength and freeze-thaw cycle displayed a linear negative correlation.