Abstract: The engineering properties of laterite had affected seriously in the condition of immersion which result in shear strength reduction. The factors of soaking time, initial water content, and initial dry density were considered.It goes direct shear test to study of immersion on the shear strength of laterite. The test results show that:the initial dry density is larger and the initial moisture content is smaller, soil shear strength reduction is greater.With soaking time, the laterite with different initial dry density or initial moisture content have different change trend on shear strength.Damage-coefficient is a measure of damage effect of shear strength in soaking condition.After immersion in lateritic samples under the softening and dissolving action of water, bring among soil particles cementation severely damaged, cohesive force decreased dramatically;Meanwhile shear test produces instantaneous compression and deformation.The original pores of laterite was filled. Laterite particles of joining-up degree is improved.Particle dislocation is relatively more difficult.The angle of internal friction increased slightly.