Abstract: For the research of expansion and shrinkage characteristics of expansive rock, two typical expansive rocks, namely marl and clay rock , of Xinxiang section of the Mid-route of South-to-North Water Transfer Project are selected to perform a large-size test of expansion and shrinkage characteristics for the disturbed sample which has been screened through a 20mm sieve. A statistic analysis is conducted from test results of the undisturbed sample of marl and clay rock in this paper, and its emphasis is to research the regularity relationship among the initial water content, compaction degree and swelling-shrinking characteristics of the reconstituted samples selected from the expansive rock in Xinxiang. And the test results show that: with the increase of the initial water content, the load-less expansion rate of expansive rock presents a good linear decreasing relationship; with a higher compaction degree and load-less expansion rate and a decreasing initial water content , the impact of compaction degree on the expansion rate presents an increasing trend; with the same compaction degree, the effect of initial water content variation on the shrinking ratio is little when the initial water content is lower than the value of plastic limit, and the shrinking ratio initially presents a gently linear increase as the initial water content grows; when the initial water content is near the plastic limit value, the impact of initial water content variation on the shrinking ratio is enhanced significantly; with the same initial water content which is lower than the value of plastic limit, the influence of compaction degree on shrinking ratio is little , however, as the compaction degree increases, the shrinking ratio presents a good linear decreasing relation; the impact of compaction degree on the shrinking ratio is reinforced slightly when the initial water content is near the value of plastic limit. The regularity of shrinkage coefficient and volume contraction ratio of the expansive rock is almost the same as that of the shrinking ratio.