The　Optical　Coherence　Velocimeter　(OCV)　technology　is　a　technique　for　high-precision　displacement　and　vibration　measurement　based　on　the　principle　of　spectral　domain　optical　coherence　method.　The　key　of　this　technology　is　to　realize　nanometer　or　even　sub-nanometer　measurement　by　high　precision　frequency　estimation　method　called　as　Hanning-window　energy　centrobaric　method　(HnWECM).　This　paper　analyses　the　error　transmission　process　of　HnWECM,　and　proposes　a　calculation　method　based　on　Paserval＇s　theorem　to　establishes　the　accuracy　theory　of　HnWECM.　It　shows　that　the　variance　of　the　estimated　frequency　using　HnWECM　is　only　proportional　to　the　signal-to-noise　ratio　(SNR)　and　very　close　to　the　Cramer-Rao　Lower　Bound　(CRLB).　The　estimation　performance　of　HnWECM　is　verified　and　compared　with　other　frequency　estimation　methods　by　simulation　and　experimental　results.　Both　the　theoretical　analysis　and　simulation　results　show　that　the　HnWECM　has　good　statistical　efficiency　and　the　best　anti-noise　stability.　This　paper　reveals　the　reason　of　chosen　HnWECM　as　the　signal　processing　method　of　OCV　technology　and　gives　its　accuracy　theory,　which　will　greatly　promote　the　application　of　OCV　technology.