The photon echo of the Er2O3-doped TeO2-Nb2O5-ZnO glass is observed on the time-delay four-wave mixing with incoherent light (TDFWM-IL) experimental setup, at the temperature 7K and with the femtosecond pulse laser of 800 nm wavelength. Moreover, the interference-beat modulation of signal intensity versus delay time is found in the experiment. According to the multi-level theory of TDFWM-IL, the experimental result is fitted with the theoretical formula when the inhomogeneous broadening is dominant. The dephasing time T2=300 fs is gotten when the fitting is the best . Then the influence of the modulation parameter c on the structure of beat frequency modulation is studied. It is found that the photon echo beat frequency modulation structure appeares at the ultralow temperature, because it is affected by the coherent effect of the coherent excited states of many sub-levels. When the temperature gradually increases, the coherent-beat modulation structure disappeares, then the feature of the photon echo is similar to the TDFWM-IL two-level system. Thus a new theoretical basis for the coherent transient spectroscopy study of the rare earth materials at low temperature is provided.