Abstract: In this paper, we do it for the loess which come from a selected embankment of Shenhe highway. With the consolidation undrained triaxial tests of controlled suction, we do it to study the law of matric suction for the effective stress strength index c and .The deformation of the selected embankment is studied by finite element analysis under the certain suction. The results showed that: the change of strength index c is obvious with the increasing matric suction. The change of strength index is not obvious with the increasing matric suction. With the increasing of matric suction, the loess strength become greater, the vertical deformation reduced slightly under certain vehicle load. The stability of embankment will improve. The conclusion of the study have certain reference significance to the actual engineering.