Abstract: Polypropylene (PP) and bamboo were selected as typical representatives of waste plastics and biomass. And the biomass and plastic co-pyrolysis weight loss, kinetic mechanism and product distribution were studied by thermogravimetric analyzer and fixed-bed reactor. The synergistic mechanism between biomass and plastic during co-pyrolysis was discussed. As the ratio of plastic increases, the ending temperature of co-pyrolysis decreases from 501 to 471℃, while the main temperature range for co-pyrolysis is shortened. What's more, the total activation energy required for the co-pyrolysis decreases when the plastic ratio is below 0.25 and then increases. Comparing the experimental with theoretical data, it is found that the synergistic effect during biomass and waste plastics co-pyrolysis is obvious. Due to the synergistic effect, the total activation energy for co-pyrolysis is much lower than calculated value. In addition, the synergistic effect can promote the conversion of macromolecular volatiles into small-molecule gas, accelerate the generation of hydrocarbons like aromatics and alkanes, and inhibit the formation of oxygen-containing substances like CO₂, phenol, carboxylic acids, furans and ketones.