Abstract: After ⁶⁰Co γ radiation, absolutely dry bamboo powder produced free radicals and its chemical composition and structure changed. Electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) techniques were used to measure the spectrum of the free radicals and X-ray photoelectron spectroscopy of the γ-ray radiated bamboo powder. The test results reveal that when the spectral splitting factor (g) of the bamboo free radicals is 2.003 3, and the intensity of free radicals increase with the absorbed dosage of irradiation according to exponential law. After irradiation of 200 kGy, the O/C atomic number ratio in the bamboo surface increases slightly, C—C and C—H content increases, C—O and CCDS1O content decreases, and —O—CCDS1O content increases to 1.5 times over that of the original, which indicates some oxygen-containing functional groups occurre and oxidation state of carbon increases in the bamboo surface.