In order to investigate the feasibility and effect of expansive soils improved by industrial waste that iron tailings sand, the basic physical properties and swelling characteristics and unconfined compressive strength of improved soil were study by laboratory test.Besides,by means of SEM,the microstructure of series of samples is studied.The result of test indicated that the marginal moisture content and plasticity index of improved soil decrease with the increase of tailings sand content; free swelling ratio and loaded swelling ratio and swelling pressure also decrease with the increase of tailings sand content.The unconfined compressive strength and cohesion increases with the increase of tailings sand content,but it decreases when tailings sand content more than 30%;internal friction angle increase with the increase of tailings sand content. It was found that the structure of improved soil in the most stable state when tailings sand content is 30% by observing the results of SEM.It is shown that the effect of expansive soils improved by iron tailings sand is obvious.So for the improvement of expansive soils provides a new method. Considering all the indicators, the optimum content of iron tailings sand that improved expansive soils should be 30%.