The 42D Rydberg atom is prepared in cesium vapor at room temperature, and the power-frequency electric field is measured based on the electromagnetically induced transparency spectrum of Rydberg atom. The 42D Rydberg atom is prepared by two-photon excitation, and the stepped electromagnetically induced transparency spectrum is obtained by changing the coupling frequency. The relationship between the spectral frequency shift and splitting of Rydberg atom under radio frequency(RF) electric field and the amplitude and frequency of RF electric field is studied. By modulating the amplitude of power-frequency electric field to RF electric field, the measurement of power-frequency electric field intensity and frequency is realized. Research results has important reference value and significance for online traceable measurement of power-frequency electric field.