To meet the requirements of high-sensitivity detection of CH₄， a greenhouse gas， this study developed a high-finesse optical feedback cavity ring-down spectroscopy technique. The influence of optical feedback on the cavity mode signal， the sensitivity of the system， and the method of spectral scanning were mainly studied. First， the optical feedback cavity ring-down spectroscopy technique was realized on a V-shaped resonator with a finesse greater than 100 000， and the difference between the cavity mode signal with and without optical feedback was compared， verifying that the optical feedback effect can improve the coupling between the laser and cavity. Second， an optical feedback detection technique with a fixed cavity length was developed， and the free spectral range （FSR） of the cavity was used as a spectral relative frequency scale. Based on a comparative analysis of the absolute wavelengths and measured relative positions of the two absorption lines in the HITRAN database， the FSR of the cavity was obtained as 0.004 2 cm^-1. Then， the detection capability of the system was analyzed using Allan variance， and the noise equivalent absorption coefficient of the system was measured to be 1.1×10^-10 cm^-1 Hz^-1/2. When the integration time was 4.7 s， the sensitivity of the system was 8×10^-11 cm^-1. Finally， a laser frequency-controlled scanning method with continuous voltage scanning was proposed. The method was verified with a standard gas of 1.5×10^-6 and a measurement accuracy of 6.8×10^-9. This method has great potential for instrument engineering.