The effect of annealing process on FMR linewidth of YIG films are studied in this paper. The micrometerthick yttrium iron garnet (YIG) films have been prepared on Gd3Ga5O12(GGG)(111) substrate by radio frequency (RF) magnetron sputtering method, and then crystallized by post annealing (750950 ℃) with common thermal annealing)and rapid thermal annealing (750-850 ℃ ) two different methods. The microstructure, the magnetic properties and the ferromagnetic resonance (FMR) properties have been investigated in detail. High quality YIG film have been obtained with RTA method in vacuum and the annealing temperature is 800 ℃.The most narrow FMR linewidths (ΔH) is 2 626.1 A/m at 9.3 GHz, the damping constant α is 2.077×10-3 and the surface roughness of the film is 1.9 nm.