Bamboo particles (BP) were treated with 0.3N (1.20 wt %) low-concentration alkali solution for different times (0.25, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 24 h) as reinforcements in poly(lactic acid) (PLA) biodegradable composites. Characteristics of BP by composition analysis, scanning electron microscopy, Brunauer-Emmett Teller test, and Fourier transform infrared spectroscopy, showed that low-concentration alkali treatment had a significant influence on the microstructure, specific surface area, and chemical groups of BP. PLA/treated-BP and PLA/untreated-BP composites were both produced with 30 wt % BP contents. Mechanical measurements showed that tensile strength, tensile modulus, and elongation at break of PLA/BP composites increased when the alkali treatment time reached 3.0 h with maximal values of 44.21, 406.41MPa, and 6.22%, respectively. Maximal flexural strength and flexural modulus of 83.85MPa and 4.50 GPa were also found after 3.0-h alkali treatment. Differential scanning calorimetric analysis illustrated that PLA/BP composites had a better compatibility and larger PLA crystallinity after 3.0-h treatment. Overall, low concentration alkali treatment was a feasible technology in creating BP reinforced PLA composites. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1667-1674, 2013