Landslide is one of the natural disasters that often occur on natural slopes. Landslides and erosion of slopes mostly happen during the rainy season, resulting in a decrease in soil shear strength. One method of reinforcing slopes is to use coconut fibers which have the features of fibers. Coconut fiber is not only relatively more economical but also can last a long time as a substitute for geosynthetics and even as a place for vegetation growth. The purpose of this study was to determine the tensile strength value of coconut fiber and to identify the shear strength of barren slopes and bush slopes on Takengon-Bintang-Blangkejeren Road, Bur Retak Area, Kampung Mendale, Central Aceh. The tensile strength testing of coconut fiber was carried out by taking into account the diameter size and the number of fibers. The tensile stress testing of coconut coir fibers was done by clamping both sides, with the diameter and the number of fibers varied. The results showed that the tensile strength (tr, MPa) of coconut coir fibers decreased with the increase in diameter and the number of the fibers. In the application, coconut coir fibers placed on a barren slope in one square meter area has the potential to produce additional shear strength.