Abstract: By changing the different experimental conditions,the influence of change of the cathode voltage on the generation of the hot electrons was studied by using the Frank-Hertz experimental measuring instrument of the University of Electronic Science and Technology of China.Through the analysis and comparison of different data processing methods and the relative atomic theory,the first excitation potential of the atom was measured more accurately,and the error of the first excitation potential measured in the experiments was explained.In this paper,the first excitation potential of argon atom is measured by different data processing methods from different aspects and different angles,and the results is corrected because of the presence of contact potential difference.A more reasonable explanation is given from the contact potential difference and the metastable state of the atomic energy level.Through this experiment,we can understand the changes in the microcosmic world from the macro voltage-current curve,enhance students' understanding of Bohr's atom theory,and exercise the students' ability to do the work and thinking ability of the image.