The work aims to explore the effect of different polylactic acid substrates on the basic performance of pol-ylactic acid/thermoplastic starch blended composite films, and screen the polylactic acid substrates which are suitable as the raw materials. Three kinds of polylactic acid (REVODE 101, REVODE 110 and REVODE 711B) were selected as the substrates and blended with the thermoplastic starch to prepare the composite films through hot pressing. The dynamic thermomechanical properties, mechanical properties, moisture permeability, water solubility and water content of the composite films were characterized. The results showed that the composite film prepared with REVODE 110 had the highest glass transition temperature (tg) compared with the others, and the tg was 36.16 ℃ when the mass fraction of plasticizer acetyl tributyl citrate (ATBC) was 20%. Then, it had the best stability at room temperature. What's more, its mechanical properties, moisture permeability and water solubility were similar to those of REVODE 101, but much better than those of REVODE 711B. The transmittance of these three composite films was similar, which was all around 14% (T600). REVODE 110 is the most suitable polylactic acid substrate for polylactic acid/starch composite films.