Aiming at the problem that the mapping relation between cavity misalignment parameters and cavity loss is unclear, and the relative cavity offset is not clear during the cavity tuning process, this study proposes a cavity loss optimization method based on cavity misalignment parameter scanning. In this method, the scanning optimization of the tilt adjustment of the cavity mirror was carried out. Similarly, the optimized cavity state of the relative misalignment between the initial cavity and test cavity was determined based on the ring-down time of the optical cavity. The experimental results reveal that there is an improvement in the measurement repeatability accuracy of the six experimental measurement results of the same high reflectivity sample, from 1.26×10^-4 to 9.83×10^-6. Furthermore, the measurement repeatability peak-to-valley value increases from 3.25×10^-4 to 2.7×10^-5 compared with the traditional method. Thus, the results verify that the proposed method can obtain a cavity tuning state with less relative cavity misalignment, which improves the optical cavity ring-down measurement system with low-initial cavity reflectivity.