In the case of a highway, a weak subgrade results in a greater thickness of pavement layer, which increases the cost of pavement construction. As the subgrade soil is too weak to bear the load, engineering solutions such as replacement, chemical stabilizations, geo-reinforcement using geosynthetics which are earlier used in sub-grade improvement. This paper discussed regarding the effects of Nylon fiber and Lime on the CBR value and CBR swelling of a weak sub grade soil. A series of CBR tests were conducted on samples of reinforced soils with different percentages of randomly distributed nylon fibers. The soil samples were prepared with and without fiber reinforcement. The percentages of fibers by dry weight of soil were 1%, 1.5%, 2%, 3%, and 4% and the aspect ratio (fiber length of 20 mm and 40 mm, and the diameters were 0.4 mm and 0.6 mm). Keeping 2% NSF constant, 1%, 1.5%, 2% and 3% lime was added and CBR value and CBR swelling were measured. Field density, natural moisture content, particle size distribution, Atterberg limit, specific gravity, Proctor test, and soaked California bearing ratio (CBR) tests were performed. The effects of nylon fiber on CBR and swells of the soil evaluated, by varying its contents and aspect ratios of the fiber. Results showed that as increasing in fiber content and aspect ratio, CBR value increases and CBR swelling decrease. It was also observed that increasing the diameter and length of nylon fiber further increases the CBR value of reinforced soil due to the interlocking/interactions between the soil particles and the fibers and also the friction generated between the soil and fiber will increase as contact area increase. Fiber content of 2% for an aspect ratio of 66.67 (length = 40 mm, diameter = 0.6 mm) is the optimal value form other trial test results. Keywords: - Weak Subgrade Soil, Nylon fiber, Aspect ratio, CBR,Lime.