Alkalization is the process of removing the hemicellulose content contained in the fiber by using NaOH liquid. Bleaching is the process of removing the lignin content contained in fiber using H2O2 fluid. The purpose of the chemical treatment in the study is to raise the tensile strength in its utilization to be applied in the form of the product. Specimens derived from kenaf natural fiber measuring 20cm x 20cm. The kenaf fiber is treated with alkali process with content (5% NaOH) and heated using temperature 1000 C for 1 hour. Then proceed with bleaching processwith content (NaOH 0,25% + 3% H2O2) and heated using temperature 600 C for 1 hour. The test is a tensile test. The result of tensile testing, the average tensile tress value of raw material has a tensile strength of 15,16 Mpa. The tensile strength of alkaline specimens is 28,73 MPa and the tensile strength of specimens of alkali bleaching specimens of 24, 98 Mpa. From these reults it can be concluded that chemical treatment of fiber can increase the value of tensile strength