Using the contractometer, shrinkage experiments were performed on expansive soil improved with weathered sand through wet-dry cycles to study the variation law of the shrinkage indexes of the improved expansive soil. Based on investigation of the changing characteristics and mechanism of the linear shrinkage rate, volumetric shrinkage rate, shrinkage coefficient, shrinkage limit, and expansion-shrinkage ratio of experimental specimens through wet-dry cycles, a formula for calculation of the shrinkage limit of the improved expansive soil with different numbers of wet-dry cycles was established. Some conclusions are drawn from the test results: the linear shrinkage rate and volumetric shrinkage rate gradually decreased with the increase of the number of wet-dry cycles, and tended to be stable after four wet-dry cycles, with maximal reductions occurring when the mixed amount of weathered sand increased from 0 to 20%; the shrinkage coefficient decreased exponentially with the increase of the number of wet-dry cycles, and tended to be constant after four or five wet-dry cycles; the shrinkage limit increased by a quadratic function with the numbers of wet-dry cycles, and the increment of the shrinkage limit gradually decreased with the increase of the mixed amount of weathered sand through wet-dry cycles; the expansion-shrinkage ratio gradually decreased and tended to be stable with the increase of the number of wet-day cycles, and the value of the expansive soil decreased significantly by mixing with weathered sand, which allowed the expansive soil to meet the standard of embankment filling.