In the off-axis integrated cavity output spectroscopy (OA-ICOS) technology, the suppression of cavity mode noise remains the primary challenge in enhancing the sensitivity of trace gas detection. The paper addressed two critical limitations in the existing OA-ICOS system: the absence of specific theoretical guidance for cavity parameter design and the reliance on empirical adjusting to suppress cavity mode noise. To overcome these limitations, we proposed a micron-level precision cavity regulati