A lactic acid polymer composition comprising formulating 100 parts by weight of a mixture consisting of 80-95% by weight of an L-lactic acid polymer having an L-lactic acid proportion of 75% or more and 5-20% by weight of a plasticizer selected from the group consisting of a polyhydric alcohol ester and a hydroxypolycarboxylic acid ester, 0.1-5 parts by weight of an anti-blocking agent having a SiO.sub.2 content of 90% or more and an average particle size of 7-50 nm, and 0.1-2 parts by weight of a slip agent; a molded product and film obtained from the composition; and a preparation process of the same are disclosed. The molded product and film are excellent in processability, transparency, flexibility, anti-blocking property and slip, and can be degraded into harmless water and carbon dioxide under natural environment, when abandoned.