Abstract: This paper presents laboratory tests for lime as modifying agent in compaction of expansive soils. The expansive soil samples are from the proposed airport location at An-Kang. The CSK-V1 multi-function electric compaction instrument is used in laboratory for heavy compaction tests. A series of compaction characteristic tests are conducted. Findings are as follows:(1)As lime dosage increases, the maximum dry density decreases, and the optimum water content increases.(2)In the vicinity of the optimal water content, as lime dosage increases, the effect of water content on dry density decreases.(3)The higher soil height, the smaller dry density in the condition of the same compaction work, lime dosage and water content.(4)Maximum dry density tends to decrease steadily as braised material time increases, which changes little after 48h. (5)The order of main influential factors of dry density is water content, the materials humectation time and the excess soil height with the same kind of lime dosage. Finally, depending on the Scanning Electron Microscope(SEM),the lime-treated expansive soil and compaction test are described and analyzed from the microscopic point of view.