The invention discloses a preparation method of a carbon electrode material of a porous structure sodium-ion battery. The preparation method comprises the steps of firstly, washing leaves of cirsium segestum with deionized water, and carrying out freeze-drying and grinding to obtain ground dried leaves of cirsium segestum; secondly, placing an activator and the ground dried leaves of cirsium segestum into distilled water according to a mass ratio of (0.5 to 5):1, stirring to form mixed suspension, then performing a hydrothermal reaction, and after the reaction is ended, concentrating the obtained mixture to obtain a slurry product, wherein 1 to 5g of dried leaves of cirsium segestum is added into each 50ml of distilled water; then carrying out calcination on the slurry product in protective gas to obtain a calcined product; and finally, removing the activator in the calcined product, then washing the product with deionized water, and until filtrate is neutral, carrying out drying to obtain the carbon electrode material of the porous structure sodium-ion battery. The carbon material prepared by the preparation method disclosed by the invention has a large specific surface area and a unique three-dimensional pore structure, shows excellent electrochemical performance, and is simple in preparation process, low in cost and easy to implement industrialization.