The work aims to prepare the polylactic acid biodegradable film material with high toughness by adding poly(butylene adipate-co-terephthalate) (PBAT) with good toughening performance and polyethylene glycol (PEG) as a compatibilizer and dicumyl peroxide (DCP) as a compatibilizer. Taking polylactic acid as the matrix, using a twin-screw extruder to melt and blend PLA, PBAT, PEG and DCP, then extrude and pelletize, and then extrude by casting to obtain polylactic acid film materials in different proportions. The mechanical properties, transparency properties, crystallization properties and micro-morphology of PLA biodegradable film materials were analyzed. The research shows that the compatibility and toughness of PLA are improved and the addition of PBAT and PEG improves the crystallization ability of PLA, while DCP weakens the crystallization ability of PLA. When the optimal mass ratio of each component in the PLA/PBAT/PEG/DCP film material is 80∶10∶10∶0.03, the longitudinal and transverse elongation at break of the material are 353.61% and 335.37% respectively, which is 42 times higher than that of pure PLA. The longitudinal and transverse tensile strengths are 35.31 MPa and 32.09 MPa respectively, and the light transmittance is 84.69%. Under this ratio, the cross-section surface of the PLA/PBAT/PEG/DCP film material presents a uniform morphology, and no obvious PBAT particle dispersed phase can be observed. Obviously, the synergistic compatibilization effect is the best, and the toughening and light transmittance enhancement effect of PLA is remarkable. Therefore, a high-toughness polylactic biodegradable film can be obtained, making the composite material not only have good toughness but also have a relatively high light transmittance, broadening its applications in the packaging field and modern industrial fields.