In this paper the polypropylene fiber was chosen as the additive material to know how it is effect on the soil stabilization, which it is used as additive for concret mixture; the polypropylene fiber is inert material and does not interact with water. The paper studies the addition of this material to a silty clay soil and its effect on the consistency limits, shear strength and compaction of the blended materials. The results show that there is an improvement in the shear strength only when the addition of the rate 1% and 2%from soil weight; either the effective of the consistency limit it was increasing the water content with increasing the rate of the addition material, because it have drink of water. At the compaction test it was founded that the increasing in dry density at the addition of 1% and 2% and reducing its value at the addition of 3% with increasing of water optimization.