Abstract In this study, WF (wood fiber)/PLA (polylactic acid) composites were pyrolyzed to study the synergistic effects during co-pyrolysis of WF-PLA blends. The co-pyrolysis kinetics, mechanism of synergistic effects and products distribution were studied by TG-FTIR-MS and Py-GC/MS. Through the analysis of co-pyrolysis kinetics, it was found that the activation energy of WF-PLA blends was lower than that of sole WF or PLA. The pyrolysis activation energy of 30%wt WF/PLA composites decreased by 70 KJ/mol compared to sole PLA. TG-FTIR-MS and Py-GC/MS analysis showed the production of lactide increased significantly accompanied by a decrease in acetaldehyde and CO during co-pyrolysis. The interactions between WF and PLA promoted the positive synergistic effects. The synergistic effects essentially promoted the free radical reaction of the PLA during co-pyrolysis, thereby reducing the activation energy of the co-pyrolysis and obtaining more recoverable lactide. This work provided a reference for the reuse of waste PLA and WF in energy field, and provided a solution to the potential PLA pollution.