Abstract: Aiming at the problem that the compactness of earthworks in Jiangxi varies in the later tests on lateritic clay embankment, this study has explored swell-shrink properties and mechanism of typical compacted lateritic clays under natural dry-wet cycling by applying a continuous swell-shrink procedure on the same soil sample, and conducted an analysis on the biases of compactness tests. The results indicate that in the case of natural dry-wet cycling, compacted lateritic clay shows significant shrinkage and swell. When no load was applied, the soil sample swelled obviously, and its absolute swell ratio increased with an increase in cycling times, reaching a peak swell ratio of 12.88%. Application of loads made a soil sample compressed: the greater load was applied, the more significant the compression was; an increase in cycling times under loading condition caused greater compression. Thus, in assessing construction quality, we must consider that compactness tests of lateritic clay earthworks performed in the later stages have biases significantly greater than those tested in the initial stage at the time of construction. In addition, similar biases will occur if dry-wet cycles are applied. A method for reducing the biases is suggested in this paper.