Polylactide (PLA) was first toughened with methyl methacrylate-butadiene-styrene (MBS) copolymer, then the toughened PLA was further blended with polydiethylene glycol adipate (PDEGA) using a twin-screw extruder. Finally, the extruded samples were blown by blown film technique. The mass fraction of PDEGA was fixed to 8%, and the ratio of PLA and MBS was changed. Mechanical properties, optical properties and rheological properties were studied, the fracture morphology of the film was observed by SEM, and the crystalline morphology of PLA was observed by POM. The results show that T_g of PLA is decreased by nearly 8 ℃, and T_cc of PLA is decreased about 17 ℃. With the continuous addition of MBS, the tensile strength is above 25 MPa, tear strength is above 120 kN/m, the elongation at break of PLA film is increased from 3.5%(pure PLA) to 40%, the modulus and viscosity also increase. With the increase of MBS content, the boundary of PLA spherulites gradually becomes blurred, the number of spherulites are increased, the spherulite size decreases obviously. The addition of PDEGA and MBS does not change crystallization types of the PLA matrix. The PLA/PDEGA/MBS films maintain good transparency and degradability.