Stabilization by using natural fiber is a cost-effective and eco-friendly method to improve properties of black cotton soil. In this research paper, the stabilizing effect of natural fiber (coconut coir) on properties of soil has been studied. From the last many more decades the use of waste material and fiber for improving properties of soil has been recorded. By keeping this in view an experimental study was conducted on locally available black cotton soil of Jalgaon District, Maharashtra state region. This Black cotton soil was mixed with different percentage of coir fiber. In order to achieve the objectives of study detailed laboratory tests were conducted on virgin black cotton soil sample and fiber reinforced sample. Tests were performed on different fiber content in different proportions so as to achieve optimum fiber content for maximum increase in bearing capacity of the soil. Coir fiber was added in different proportion of 0%, 0.50%, 0.75%, and 1% individually. It was found that after adding coir fiber at 0.5%, accompanying clayey soil, O.M.C changes from 18.32% to 15.22% and MDD changes from 1.85 g/cm3 to 1.87 g/cm3.C.B.Rratio from 2.12% to 6.71% and U.C.S value of natural soil was 1.07 kg/cm2 on increasing coir fiber UCS value increase till 0.75% of coir fiber to 1.35 kg/cm2.