Because of its special features that are soft, elastic, good absorption capacity and corrosion resistant, cotton fiber has widely been used in daily life. People usually use cotton to make yarn, cosmetics and health supplies. Cotton fibers have not been used specifically by utilizing it is potential for mechanical properties to resist compressive loads as materials for structures. This study was conducted to determine the compressive characteristics of composite materials at various fiber content. Cotton fibers were spun as well as untreated and alkaline treated with 5% NaOH. The fiber volume fraction was varied at 0,5,10,15 and 20 vol%. This study used unidirectional spuri cotton fibers and polyester matrix, easted in a press mold. Specimens for compressive testing were made according to the ASTM D3410 standards. Cross-sectional photo macrograps were analyzed using the imageJ open source sofware to determine the actual fiber fraction. The actual fiber content of the untreated compressed test specimens were obtained 0%, 4.6%, 7%, 11,2%, and 16,7%. Those for the NaOH treated were obtained 0%; 3,8%, 6,8%, 9,4%, and 17,4%. Composite at Vf = 0% have the highest compressive strength of 135,4 MPa, and strain value of 0,216 mm/mm and an elastic modulus of 1.398,2 MPa. Those with NaOH treated fiber have a higher compressive strength than without treatment, ie at Vf = 3,8% at 122,7 MPa with a strain value of 0,186 mm/mm and an elastic modulus of 1.551,6 MPa.