Abstract: Adding CaO，MgO and ZnO in the biodegradable poly( L-lactic acid) (PLLA) respectively，the effect of these metallic oxides was investigated in the soil supernatant of Shannxi local soil . The chemical structure before and after degradation of PLLA was characterized by FT-IR spect rum，The results show that the pure PLLA film and the PLLA films adding with metallic oxides can be degraded in the soil supernatant，and the adding of CaO and MgO can fasten the degradation rest of PLLA. The microscope observation shows that more remarkable defect and microbiology erosion trace occurred on the surface of PLLA films adding with CaO,MgO after degradation.