The work aims to study the effect of carbon nanotubes and graphene on the electrothermal properties of composite carbon-based conductive ink, and develop conductive ink with excellent properties. The effects of carbon nanotube diameter size, different ratios of carbon nanotubes to graphene, carbon mass fraction in the ink and coating thickness of the ink on the conductivity of the composite carbon-based conductive ink were investigated, and the corresponding prediction models for each influencing factor were fitted based on the experimental data. The preferred ratios of the ink were determined, and the conductive ink coating prepared according to the preferred ratios were tested for electrical and thermal conversion. The conductive ink coating prepared with graphene and multi-walled carbon nanotubes with a diameter of 25 nm as conductive filler had the best overall conductivity. When the carbon mass fraction in the conductive ink was 2.5% (MWCNTS-0.125%, graphene-2.375%), the amount of water-based acrylic resin added was 5.25%, the coating thickness of the ink after curing was 0.147 mm, the electrical resistivity of the ink conductive coating was 0.089 3 Ω.cm. The power was 13.49 W under the condition of external voltage of 5 V, and the working time from room temperature to 100 ℃ was only 13.723 s. The heating uniformity of the ink coating met the requirements of national standard JG/T 286-2020. The ink coating prepared according to the preferred ratio builds up a uniform and rich conductive network inside the ink, which greatly enhances the conductivity of the ink and contributes to the excellent electrothermal property of the ink.