This work was aimed to obtain polylactic acid films with good barrier properties and thermal stability. Graphene was added into polylactic acid to modify it. Graphene oxide was prepared using the flaky graphite by the improved Hummers method. Graphene oxide was reduced to graphene by thermal stripping method. Grapheme/ polylactic acid films were prepared with tape casting method, using polylactic acid as the substrate and graphene as the reinforcement. The structure, thermal stability and barrier properties of films were tested. Infra-red spectrogram showed that graphite intercalation compound with COOH, C＝O, C—O—C and C—OH functional groups was formed when graphite was oxidized by the strong oxidizer, and graphene stripped sufficiently by reduction. The thermal stability performance and barrier properties of graphene and lactic acid composite films increased with the increasing graphene content. Within the scope of the test parameters, the thermal stability and barrier performance of the graphene/PLA composite films were better than those of polylactic acid film.