The invention relates to a green and environmentally-friendly synthesis method and an application of polypyrrole. The method comprises the following steps: S1, mixing an acidic solution with a pyrrolemonomer, and performing uniform stirring; S2, adding an oxidizing agent to a uniformly mixed solution obtained in step S1, performing uniform stirring, and standing the obtained solution for a periodof time; and S3, filtering the mixed solution after standing, and washing and drying the obtained product to obtain the black solid polypyrrole. The synthesis method of the invention is simple, greenand environmentally friendly, and is suitable for industrial application; and the polypyrrole synthesized by the method is suitable for being used as an adsorbent, can directly capture CO2 in humid flue gas without pretreatment for removing moisture in the flue gas, so the polypyrrole is green, and saves energy.