Half-wave rectifier is widely used in teaching as one of the applications of diodes, but it has not paid enough attention to the experimental phenomena of the cut-off state characteristics of diodes. Compared with the resistance-capacitance filter of half-wave rectifier, inductance filter is seldom mentioned to arouse interesting of students for knowledge. Therefore, based on the experimental results of Multisim 10 simulation software, it is verified that the cut-off state of the diode has the characteristics of fixed capacitance, and the influence of the ratio of filter inductance to load on the filtering effect is analyzed.