According to basic assumptions about the ideal operating state of p-n junction diode, deducing the relation of the time dependence of constant on the parameters such as diode size, diffusion length, carrier lifetime and alternating current frequency etc. at the base and near the p-n junction interface when diode is working under the applied alternating current. From the results,we discovered that in the two kinds of states of low and high current frequencies, the diode characteristics act on the time constants differently. In the low frequency state, the time constant is related to the material characteristics but not to applied current frequency. But in high frequency state, the time constant has no relation with the material characteristics, and was only related to the applied current frequency.