Abstract: The overconsolidated unsaturated soils emerge in many engineering projects. The constitutive models for unsaturated soils are very complicated due to the complex mechanical beahviour of overconsolidated unsaturated soils. A modified constitutive model is given considering the effect of overconsolidation. The constitutive models for the overconsolidated unsaturated soils are used to solve complicated non-linear problems. The implicit integration algorithm of a hydro-mechanical constitutive model for overconsolidated unsaturated soils is given. The consistent tangent modulus is also given. The implicit integration algorithm is validated by the experimental data available in the literatures. The algorithm is applied to the finite element method to analyze an unsaturated soil slope.