In order to improve the interfacial interaction between poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate) (PETG) and bamboo flour, the surface of bamboo flour (BF) was modified with methyl methacrylate (MMA) using the electron transfer (AGET) atom transfer radical polymerization (ATRP) method. The grafted BF was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis. The MMA groups had been successfully grafted onto the BF surface and the contact angle of the grafted BF was as high as 130°. The maximum flexural strength was determined to be 72 MPa for the composite containing 20 wt% modified BF, which was higher than that of the composite containing 20 wt% original BF (62 MPa). Also, the decrease in loss factor indicated that the grafting modification improved the compatibility between PETG and BF, and this conclusion was also confirmed by SEM. The results have great practical significance for the application of PETG/BF composites.