The diffusion characteristics of Ga in SiO2 films and at the interface of SiO2-Si is characterized and analyzed by means of SIMS, SRP and AFM respectively. The results indicate that the new element Ga born of pyroreaction of H2 and Ga2O3 is absorbed rapidly by SiO2 films and reach the interface of SiO2-Si, its absorb-export flux is directly proportional to doping time under a certain condition; Ga diffuses effectively in the Si body according to solid-solid diffusion principle at the interface of SiO2-Si and depend on the higher solubility in Si; by well combination of the too above mentioned, Ga diffused into the Si body through ideal surface and gained diffused result of high homogeneity and high repeatability.