The invention discloses a preparation method of a novel hyperbranched triazine char forming agent, which comprises the following steps: adding a dissolved diamine solution at 0-10 DEG C, gradually and dropwisely adding a dispersed cyanuric chloride solution, and reacting for 1-4 hours; heating to 30-70 DEG C, adding an acid-binding agent, and reacting for 3-8 hours; heating to 90-150 DEG C, and reacting for 6-10 hours; and stopping stirring, carrying out vacuum filtration, washing with water, and drying to obtain the triazine hyperbranched char forming agent. Compared with the prior art, the invention has the advantages of continuous reaction process, short reaction time, cheap raw materials, low solvent consumption, no addition of any blocking agent in the reaction process, simplified synthesis technique, high heat stability and high char forming ratio.