The Stark effect in Rydberg atoms exhibits remarkable sensitivity to external electric fields, thus forming the fundamental basis for precision electric field measurements. This study systematically and comprehensively investigates the regulatory effects of DC and AC electric fields on cesium Rydberg atoms, both experimentally and theoretically. Utilizing a two-photon three-level system, we generate 28D_5/2 Rydberg states and establish electromagnetically induced transparency (EIT) as the macroscopic observable. Our experimental results demonstrate distinct Stark splitting patterns under DC fields, revealing three fine-structure states each with polarization-dependent frequency shift,they being the negative polarizability states (m_j = 1/2, 3/2) exhibiting rightward shifts, and the positive polarizability state (m_j = 5/2) showing leftward displacement. For power-frequency AC fields (50 Hz), we observe characteristic double-frequency modulation of the EIT-Stark spectra, with measurement limitations emerging at field strengths above 24 V/cm due to laser scanning range constraints. To overcome this limitation, we develop an innovative DC field regulated measurement scheme, establishing a dynamic model for the combined AC/DC field interaction with Rydberg atoms. The model successfully derives demodulation expressions for extracting both DC and AC field components from the composite spectral shifts. Experimental validation shows that applying an 8 V/cm DC bias field can extend the measurable AC field range to 32 V/cm, achieving a 33.3% improvement over direct measurement methods within a 1 GHz laser scanning range, while maintaining exceptional accuracy with demodulation errors below 0.8% across all tested configurations. The detailed error analysis reveals that the measurement precision improves with the increase of field strength, with a standard deviation of σ = 0.2196%, demonstrating the robustness of our approach. Compared with existing techniques, this DC-field regulation method effectively addresses the critical challenge of limited laser scanning range in strong-field measurements, while preserving the quantum advantages of Rydberg atom sensors. The research provides both theoretical foundations and practical solutions for measuring power-frequency strong electric fields in power systems, with potential applications extending to other low-frequency strong-field measurement scenarios. Future work will focus on enhancing measurement stability in extreme field conditions, improving accuracy, and further expanding the operational range of this quantum sensing technology.