Abstract: The laterite is prone to aggregates due to the possession of high-content clay and moisture. It may be difficult to mix uniformly when lime and/or cement is added into the laterite, and further influences the treated effects. Four groups of laterite are selected, with the aggregate sizes of 5.0, 2.0, 1.0 and 0.5 mm, respectively. The mixing ratio of metakaolin-lime-laterite is 5∶5∶90 in dry weight. Then, the mixtures are moistened to the predetermined water content of 33.2% using distilled water. Finally, the hydro-mechanical performances and microstructure tests on the laterite specimens are carried out after compacted and cured to predicted periods. The results show that the linear shrinkage increases and the unconfined compressive strength decreases with the increasing of the aggregate size of the treated laterite. However, the inhibition of the shrinkage and the enhancement of the strength appear after adding metakaolin into the treated laterite with the same aggregate size. This may be ascribed to the following reasons, lime just adheres to the surface of the laterite aggregates, which only forms "bridging" linkage between the aggregates, and does not develop enveloping cementation. The metakaolin, containing plenty of amorphous silicon and aluminum oxides, can quickly capture the calcium ions in calcium hydroxide solution and form cementation hydratessilicon and calcium aluminate owing to having high pozzolanic activity. Meanwhile, the metakaolin also play a role of filling into the inter-pores of soils. Both of them improve the hydro-mechanical performances of the treated laterite.