In order to improve the dispersion of kenaf fibers, hydrogen peroxide (H2O2) presoak combined with steam explosion degumming was carried out. The experiment of microstructure characterization, chemical composition analysis, and crystallinity were analyzed. The single factor experiment results showed that the optimal H2O2 presoak/steam explosion conditions are as follows: concentration of H2O2 in 0.6 mol/L, presoak time in 1 h, steam pressure of 1.2 MPa, and steam pressure maintaining time of 60 s. Optimized fiber fineness can reach 180 with the breaking tenacity of 5.28 cN/dtex. It is approximately double compared with kenaf fiber treated by distilled water/steam explosion. It can be found that steam explosion presoaked with H2O2 can remove the non-cellulosic materials like hemicellulose and lignin effectively, make the fiber surface clean and smooth, and increase its crystallization index without destroying the crystal type of kenaf cellulose.