A method of improving surface flame resistance of a substrate is provided. A substrate is provided. An atmosphere pressure plasma process is performed on the surface of the substrate to form an inorganic film layer on the surface of the substrate, wherein a process gas of the atmosphere plasma process includes a flame resistance precursor, a carrier gas, and a plasma ignition gas. Particularly, the flame resistance precursor is selected from a siloxane compound, an inorganic alkoxide compound and a combination thereof. The siloxane compound has a formula of Si(OCnH2(n+1))4, n=1˜5, and the inorganic alkoxide compound has a formula of A(OCmH2m+1)4, where A represents Sn, Ti, Zr, Ce and m=2.