In　situ　measurement　of　particle　flow　is　a　promising　tool　to　visualize　how　the　particles　affect　the　power　feeding　laser　additive　manufacturing　(PFLAM).　A　simple　and　robust　platform　based　on　optical　feedback　interferometry　(OFI)　was　implemented　in　this　study.　The　diameters　of　particles,　the　change　of　particle　density,　and　the　agglomeration　behavior　of　particles　in　the　powder　stream　generated　by　the　powder　feeder　can　be　measured　through　in　situ　measurements　based　on　the　OFI.　Signal　detection　and　data　processing　became　more　difficult　when　the　particle　diameter　was　much　larger　or　much　smaller　than　the　detection　laser　wavelength.　The　distribution　of　particles　in　fiber　laser-induced　plume　with　a　diameter　ranging　from　0.3　mu　m　to　4　mu　m　can　be　measured　using　the　OFI　in　laser　additive　manufacturing　with　powder　feeding.　The　percentage　of　particles　with　a　diameter　of　about　0.65　mu　m　in　plume　decreased　significantly　with　the　increase　of　laser　power.