To　accurately　measure　the　surface　roughness　of　precision　parts,　this　paper　proposes　a　non-destructive　measurement　method　of　surface　roughness　using　frequency-domain　interferometry　as　the　core　detection　principle　and　the　Hanning　window　energy　center　method　as　the　signal　demodulation　method.　The　corresponding　relationship　between　the　height　changes　of　the　sample　surface　profile　and　the　frequency　density　changes　in　the　interference　signal　was　established,　and　the　Hanning　window　energy　center　method　was　used　to　accurately　extract　the　periodic　frequency,　which　can　more　accurately　measure　the　surface　roughness　of　the　sample.　After　the　spectrum　correction　method,　the　peak　signal-to-noise　ratio　of　the　system　reaches　50　similar　to　60　dB.　When　the　signal-tonoise　ratio　is　54.8,　the　theoretical　measurement　accuracy　of　the　system　reaches　5　nm.　The　vibration　error　generated　during　the　actual　measurement　process　is　only　20　nm.　The　measurement　results　of　the　roughness　measuring　instrument　were　compared　and　analyzed.　The　experimental　results　showed　that　this　system　has　higher　measurement　accuracy　and　accuracy,　and　the　maximum　repeatability　error　is　7　nm.　To　further　verify　the　accuracy　of　the　system,　an　atomic　force　microscope　was　used　for　comparison　and　verification.　The　difference　between　the　two　measurement　results　was　12　nm.　This　work　provides　a　faster　and　more　accurate　non-destructive　measurement　method　for　surface　roughness　measurement.