An　ap　proach　of　path　planning　for　inner　-element　uniformity　auto　-test　of　multi　-element　infrared　detector　was　proposed　based　on　a　single　element＇s　response　to　the　infrared　spot　scanning,　which　formed　the　central　line　of　the　special　distribution　formed　by　the　signal　intensity.　The　method　could　be　used　to　locate　the　element　path.　According　to　the　alignment　of　infrared　spot　and　the　center　of　sensitive　surface　of　multi　-element　infrared　detector,　the　2　-dimension　distribution　of　an　element　output　signal　intensity　was　obtained　by　infrared　spot　scanning　on　the　sensitive　surface　which　was　on　the　mobile　station　of　high　precision　6　-degree　-of　-freedom.　The　response　signal　intensity　distribution　was　analyzed;　a　conclusion　was　that　both　the　edge　points　of　a　response　signal　can　be　obtained　through　extremum　of　3rd　order　derivative.　Projecting　the　signal　intensity　distribution　on　to　a　2-dimention　image,　the　gray　intensity　of　which　was　in　accord　with　the　signal　intensity.　Every　order　derivative　of　the　projected　signal　could　be　easily　obtained　by　convolution　with　1st,　2nd,　and　3rd　order　derivative　of　Gaussian　convolution　kernel　separately,　while　the　edge　points　of　each　section　was　extracted.　The　center　points　can　be　calculated　by　arithmetic　mean　of　two　edge　points,　and　the　central　line　of　the　2-dimensional　distribution　band　can　be　fitted,　which　was　also　the　scanned　inner-element　length　direction.　According　to　this　direction　and　topology　of　elements,　the　auto　scanning　path　for　testing　the　inner-element　uniformity　was　planned.　Finally,　an　experiment　was　presented.　Results　show　that　the　proposed　approach　advances　the　efficiency　and　accuracy　of　inner-element　uniformity　testing　of　multi-element　infrared　detector.