By the method of exciton dynamics, direct formulas were deduced about the relationship between the tunneling current and the position of the tip for both single and dimer adsorbates when the purely coherent memory function is independent of time, and the application environment for these practical models were discussed. In addition, they were also used to investigate the effect of the substrate’s thickness on the scanning tunneling microscope (STM) images and interpret the STM images of Au(110) for both 2X1 and 3X1 reconstructed surfaces. The results are in good agreement with experiments and other theory.