The invention discloses a preparation method of high-temperature-resistance PTFE micro-powder for a polyimide composite. The preparation method includes the following steps that PTFE micro-powder is put in a reaction still with a stirrer, nitrogen displacement and vacuumizing are carried out, after the operation is repeated 3-5 times, and mixed gas of fluorine gas and nitrogen is introduced into the reaction still; the reaction still is heated to the heating temperature of 100-200 DEG C at the stirring speed of 20-80 rpm, treatment is carried out for 10 min to 2 h, then the reaction still is cooled to 25 DEG C, nitrogen displacement is carried out in a reactor, the PEFE micro-powder is smashed, and the high-temperature-resistance PTFE micro-powder for the polyimide composite is obtained. The process is simple, and the obtained product has the advantage of high heat stability and can meet the application requirement of the polyimide composite.