Influences of dislocation distribution on the resistive switching effect of Ag doped SiO2 thin film are investigated under different sample preparation conditions. Stable resistance switching characteristics are observed for the samples annealed at 120 ℃ and prepared in Ar/O2 mixed atmosphere. It is shown that annealing process, electric field formation and atmosphere of preparation can change the intensity and the distribution of the dislocations (Ag interstitial atoms and oxygen vacancies) in the Ag-SiO2 structure, which leads to the resistive switching effect based on the formation and annihilation of the conducting filaments.