As　a　compact　and　simple　sensing　technique,　optical　feedback　interferometry　(OFI)　can　be　a　promising　flowmetry　method　in　various　microfluidic　applications.　In　this　paper,　OFI-based　flowmetry　sensor　performance　in　a　microscale　flow　scheme　is　studied　theoretically　and　experimentally.　An　innovating　model　and　different　numerical　methods　are　investigated,　where　the　scattering　light　angle　distribution　is　involved　to　predict　the　Doppler　frequency　distribution.　For　the　first　time,　our　model　describes　the　influences　of　multiple　OFI　sensor　system　characteristics,　such　as　flowing　particle　size,　concentration,　channel　interface　reflectivity　and　channel　dimension,　on　the　OFI　signal　spectral　performances.　In　particular,　a　significant　OFI　signal　level　enhancement　was　achieved　by　deposing　a　high　reflectivity　gold　layer　on　the　rear　channel　interface　due　to　the　increased　forward　scattered　light　reflection.　The　consistent　experimental　validation　associated　with　the　simulations　verifies　this　numerical　simulation　method＇s　reliability.　The　numerical　methods　presented　here　provide　a　new　tool　to　design　novel　microfluidic　reactors　and　sensors.