Marine electric field measurement is of significant importance for monitoring marine activities and exploring seabed resources. Due to the low-frequency characteristics of marine electric field signals, weak signal measurement is inevitably affected by device 1/f noise and environmental frequency-conversion harmonic noise. Notably, the frequency of environmental frequency-conversion harmonic noise may closely approach that of the target electric field signals, making it difficult to suppress using existing chopper amplification techniques. To address the challenge of existing measurement circuits in suppressing environmental frequency-conversion harmonic noise in conventional measurement circuits, this article proposes a marine electric field measurement method incorporating switched-frequency conversion quartz crystal resonance narrowband noise suppression. The approach converts marine electric field to 32.768 kHz, and the up-converted signal undergoes ultra-narrowband filtering via a high-Q quartz crystal resonator. Theoretical analysis is conducted on the frequency-conversion tuning process of the marine electric field and the frequency-selective characteristics of the proposed measurement circuit, leading to the derivation of the expression for the output signal after frequency-conversion tuning narrowband processing. An experimental platform for electric field measurement is established, and the designed frequency-conversion tuning narrowband measurement circuit is tested. Experimental results show that when the marine electric field signal frequency ranges from 0.01 to 0.2 Hz, the sensitivity of the frequency-conversion tuning narrowband measurement reaches 2.78 times that of direct measurement, with a circuit bandwidth of less than 0.4 Hz. For a marine electric field signal at 01 Hz, the signal-to-noise ratio of the frequency-conversion tuning narrowband measurement shows a 19.82 dB improvement compared to direct measurement. This method not only enables the detection and measurement of weak marine electric field signals in strong noise environments but also provides a foundation for future deployments of marine electric field measurement arrays.