In this letter, we investigated the influence of the fast thermal treatment on the spin pumping in ferromagnetic insulator yttrium iron garnet (YIG)/normal metal Au bilayer system.The YIG/Au bilayer thin films were treated by fast annealing process with different temperatures from 0 to 800 ℃.The spin pumping was studied using ferromagnetic resonance.The surface evolution was investigated using a high resolution scanning microscopy and an atomic force microscopy.A strong thermal related spin pumping in YIG/Au bilayer system has been revealed.It was found that the spin pumping process can be enhanced by using fast thermal treatment due to the thermal modifications of the Au surface.The effective spin-mixing conductance of the fast thermal treated YIG/Au bilayer has been obtained.For the annealing temperature above 700 ℃, typical Au nano-particles appeared.These Au nano-particles induced a surface anisotropy in YIG/Au interface.