A new method to produce high toughness Poly(lactic acid) (PLA) was introduced in this study. The blends of low molecular weight triacetin (TAC) and oligomeric poly(1,3-butylene glycol adipate) (PBGA) were first used as multiple plasticizers to lubricate PLA and then the plasticized PLA cross-linked with triallyl isocyanurate (TAIC) through electron beam irradiation. In this way, a kind of stable PLA material with high elongation at break was obtained. The elongation at break of the prepared material is more than 260% with a tensile strength of 23.5 MPa when the irradiation dose is 10 Mrad. Detailed studies of Fourier transform infrared (FTIR) spectra and viscosity experiments revealed that both the self-cross-linking of the PLA molecular chains and the cross-linking between the molecular chains of PTA and PBGA could occur. This results in the remarkable improvement in the performance of the obtained materials.