Monolayers of the triblock copolymers consisting of poly(gamma-benzyl L-glutamate) (PBLG) as the hydrophobic group and poly(ethylene oxide) (PEG) as the hydrophilic one could be formed on the air-water interface. Monolayer behavior of PBLG/PEO/PBLG block copolymer is affected on the content of PEO in the block copolymer. Circular dichroism and Fourier transform infrared data showed that the block copolymer Langmuir-Blodgett (LB) films were formed as an oriented state of the polymer chains by the compression, and the in-plane orientation is also dependent on the content of PEO in the block copolymer. Atomic force microscopy showed that the packing of the PBLG LB film was found to be ordered.