Abaca,also known as Manila hemp,is native to the Philippine where it has been cultivated.It belongs to the Musasea family and is cultivated for its fibers.Abaca fibers derived from the trunk of the species Musa textilis is one kind of the natural fibers with the highest cellulose content.In this study,the effects of mechanical properties and microstructure on treated abaca fibers were shown.Alkali was adapted to treat abaca fibers in this work in order to improve their mechanical properties and the mechanism was also analysis.Fibers were dipped into aqueous solutions of sodium hydroxide at concentrations of 5%,10% and 15 wt% for 5 minutes,and subjected to single fiber tensile test and observations by a scanning electron microscopy (SEM) to assess morphological changes subsequently.The results showed that tensile strength of the treated abaca fiber was decreased.The Young’s modulus has a similar phenomenon with tensile strength.The Young’s modulus decreased over the 5 wt% alkali concentrations,too.At the 5 wt% alkali concentration the young’s modulus increased.Oppositely,the strain at break curve decreased less than the 5 wt% alkali concentration condition and increased over the 5 wt% alkali concentration.Electron microscopy imaging revealed that the fiber lumen diameter decreases and becomes distorted with concentrations increasing.