Abstract: In order to study the effect of bamboo gradient structure on the properties of bamboo bundle fiber composites, bamboo bundle fiber (BF) as the enhanced phase, epoxy resin (EP)-methyl tetrahydrophthalic anhydride (MeTHPA) system is the matrix phase, BF/EP-MeTHPA composite was prepared by thermopress molding. By changing the BF unit: yellow side (BF-YS) and green side bundle fiber (BF-GS), the effect of natural structure on the failure of interface of BF/EP composite was studied. Based on the mechanical properties of composites, through nano and micro test means such as dynamic thermomechanical analysis (DMA), in situ SEM and FTIR, the state of BF/EP-MeTHPA, interface microregion, thermal analysis and macromechanical characterization were studied. The experimental results show that due to the high fiber content and strength in BF-GS, the enhancement effect and distribution uniformity in epoxy system is better than BF-YS. But the permeability and interface performance are lower than bamboo bundle fiber of yellow side/epoxy resin-MeTHPA (BF-YS/EP-MeTHPA). Through the observation of the bamboo structure, it is found that BF-YS remains more parenchyma cells, and the rough surface favors the infiltration and adhesion of EP, so the infiltration force of BF-YS is about 60% in the contact angle test of BF-GS. FTIR shows that MeTHPA can react with BF hydroxyl groups to generate new ester bonds, making the chemical bond between BF and EP-MeTHPA system to improve the interface stability, while the exposure of the non-crystalline area of BF-YS makes its polarity stronger (106.5 mN/m), the relative area variation of the characteristic peaks is greater than BF-GS, easier to form, and the stability will also improve.