Disclosed is a method of forming a composite micropowder, including mixing 100 parts by weight of fluorine-containing polymer, 10 to 140 parts by weight of silane, catalyst, and water, such that the silane is in-situ polymerized in the fluorine-containing polymer to form a polysiloxane, and the fluorine-containing polymer and the polysiloxane form a composite. The composite is dried, and then physically crushed to form composite micropowder. The total weight of the fluorine-containing polymer and the silane and the weight of the catalyst have a ratio of 100:1 to 100:0.0001. The silane and the water have a molar ratio of 1:0.5 to 1:3. The composite micropowder has a diameter of 0.1 μm to 15 μm. The fluorine-containing polymer and the polysiloxane in the composite micropowder have a weight ratio of 95:5 to 60:40.