Abstract: The engineering charactristics of variegated colour sandy clay is special. This sandy clay has the properties of swelling, strong disintegration and corrosion. Rock mass wetheres rapidly after exavated, and as soon asthe fissure water leaked the surrounding rock loosens and softens .If the support method or measure of stabilization is not suitable the convergence of surrounding rock will last. That ,will lead to the failure of primary lining and affect the construction safety and progrersj. This article analyses the engineering charactristics and deformation mechinsm of variegated colour sandy clay be the example of trestment method'of the clay in' tunnel coustruction, and illestrates the construction technique of the variegated colour sand clay.