To improve the thermal stability and mechanical properties of poly(lactic acid) (PLA), bis(tert-butyl dioxy isopropyl) benzene (BIBP) (0-0.4wt%) as cross-linking agent was introduced into the PLA. The PLA/BIBPx samples were characterized by Fourier transform infrared spectrometry. The gel fraction and degree of swelling of PLA/BIBPx were studied. The thermal and degradation properties of samples were also investigated by means of differential scanning calorimetry and thermogravimetric analysis; the thermal stability of the samples was improved by the addition of BIBP. The complex viscosity (*), storage modulus (G), and loss modulus (G) were increased with the increase in BIBP content from rheological measurement. The mechanical properties of the PLA/BIBPx blends and PLA/BIBPx films were tested by tensile tests, and the blends' tensile strength was enhanced due to the cross-linking effect of BIBP. The 0.2wt% BIBP gave the PLA/BIBPx blends the best mechanical properties, while the 0.1% BIBP made PLA/BIBPx films an optimal mechanical property. The morphology of the tear-fractured surface of the films was also studied, and PLA/BIBP0.1 film revealed more clearly layered structure than PLA.