Natural fibers are considered to have potential use as reinforcing material in polymer matrix composites because of their good strength, stiffness, low cost, environmental friendly and biodegradability. Elephant grass (TyphaAngustata) fiber is used as new natural fiber reinforcement and polystyrene as matrix. TyphaAngustata fibers (TAF) were extracted and used to prepare sodium hydroxide treated and untreated TAF reinforced polystyrene composites. Composites were prepared with randomly oriented fibers with different proportions of fibers and matrix ratio. Different types of compression molded TAF-polystyrene composite were prepared using different weight percent of treated and untreated TAF with compositions 5, 15, 20, 25 and 30 wt. % in polystyrene. Mechanical tests i.e. impact and hardness tests were performed. The results showed that, as the fiber volume fraction and composite post curing time increases the mechanical properties of the composite increases.