This research was aimed to investigate the effect of $K_2CO_3$ instead of NaOH on retting of the kenaf bast. We examined the relationship between separation of fiber bundle and tensile strength besides observing the color, handle and cross sectional view for the kenaf fiber retted with various concentration(100, 150, 200, 250, 500, 1000mmol) of $K_2CO_3$ and double retted with 0.5% pectinase after $K_2CO_3$ retting. The one retted on low $K_2CO_3$ concentration, $150{sim}200mmol$, showed the best result on color, handle and luster. The separation of fiber bundle started even at the low $K_2CO_3$ concentration, 100mmol, and as the $K_2CO_3$ concentration was higher, the size of the fiber bundle was smaller. In the case of 1000mmol, the fiber bundle became irregular, but they were breaking up into certain way. Regardless of $K_2CO_3$ concentration, the thinner the diameters of the kenaf fiber bundle, the stronger tensile strength have appeared. This result corresponds with the result of cross sectional view. Retting on $150{sim}200mmol;K_2CO_3$ concentration was most effective on fiber bundle#s separation and tensile strength. The one with double retted with 0.5% pectinase after $K_2CO_3$ retting showed very small size of fiber bundle and low tensile strength compare to the one just retted on $K_2CO_3$. This decrease of tensile strength seem to be related to damage of the fiber resulted by excessive fibrillation.