Abstract: This paper addresses the limitations of traditional coupler reciprocity methods in calibrating hydrophones, such as size constraints and material restrictions, aiming to enhance calibration accuracy. A transfer coupler reciprocity method is proposed for hydrophone sensitivity calibration, addressing issues like varying coupler volume parameters for different hydrophones. The principles of this method are detailed, and both reference and transfer couplers, including three-transducer and four-transducer types, are developed. Calibration standards based on this method are established, and calibration experiments for standard hydrophones in the 20 Hz to 2 kHz frequency range are conducted using both types of transfer couplers. The results from these two couplers are compared, showing good consistency, and measurement uncertainties are evaluated. To verify the calibration accuracy, results are compared with those from a low-frequency underwater sound primary standard. The deviations are found to be within 0.5 dB, less than the total uncertainty of the comparison devices, validating the accuracy and achieving a measurement uncertainty of 0.4 dB (k=2). By integrating reference and transfer couplers, traditional challenges in coupler reciprocity calibration are overcome, improving accuracy and laying the foundation for higher-level low-frequency underwater acoustic standards.