Abstract: With the continuous deepening of the "dual carbon" policy and the "bamboo instead of plastic" initiative, the study on natural fiber-reinforced biodegradable polymer is important. However, the different polarity between natural fibers and polymer matrix leads to poor interface bonding, which affects the composite’s comprehensive performances and restricts its practical applications. In this study, bamboo fiber (BF) was pretreated by alkaline solutions to improve its interfacial compatibility with poly(butylene adipate-co-terephthalate) (PBAT). And, the effect of interface reinforcement on the comprehensive performances of bamboo/polymer composites (BPC) was explored. Also, focusing on the changes in physical structure and chemical component of BF, the mechanism on improving properties of the composites was proposed. The composites incorporating 6 wt.% alkali-treated BF exhibit optimal comprehensive performances, the tensile strength, flexural strength and impact resistance were increased by 48.81%, 28.88%, and 37.5%, respectively. The thickness swelling and water absorption decrease by 43.6% and 28.9%, respectively. The etching effect on the fiber surface promoted the formation of mechanically interlocked structure and partially degradation of chemical components could reduce surface polarity differences, which synergistically improved the interfacial bonding between bamboo fibers and polymer matrix. This study could facilitate the potential applications of the biodegradable composites in the fields such as biomedicines, intelligent construction and functional packaging, which shows the contribution to the construction of ecological civilization.