By applying the conception of image force acted on dislocation by free surface in solid physics,in this paper the following topics have been dis-cussed.the effects of adjustmentary elements on the creep fracture of the fault in earthquake source,the propagation of creep slip just before earth-quake in the locked fault and unsteady propagation of crack when earth-quake occurs.The formulas of the image force acted on screw and edge dislocations by sevral different shape free-boundaries have been derived.As an example,the additional stress field on the fault due to the image force of free surface when the relative displacement of a section of the fault in earthquake source occurs bas been calculated.The order of this additional stress field has been estimated under the actual condition.We come to the conclusion that the effects of image force can not be ignored in earthquake source process,particularly,in studying the trigger effects on large earthquake.Based on the point of image force,some phenomena following when the earthquake occurs have been interpreted.Studying the dynamic effects of image force would be helpful for catching some short-term and immediate precursors imformation.