Transparent　tooth　correction　treatment　is　an　esthetic　alternative　to　traditional　orthodontic　treatment.　Recently,　attachments　were　introduced　in　transparent　tooth　correction　treatments　to　improve　the　predictability　of　orthodontic　movement.　In　order　to　optimize　the　attachment　configuration,　the　force　delivery　system　of　attachments　in　orthodontic　aligner　treatment　was　analyzed.　Based　on　mechanical　principles,　such　as　the　synthesis　theorem　of　force　system,　Varignon　theorem,　and　the　theorem　of　force　translation,　the　force　system　of　attachment　was　analyzed.　How　the　attachments　affected　the　orthodontic　treatment　was　investigated.　The　attachments＇　force　system　F　r　,　F　t　,　M　r　and　M　t　was　determined.　The　optimum　attachment　for　translation　and　controlled　tipping　movement　was　conceived.　The　attachments　can　be　designed　and　placed　appropriately　to　improve　tooth　movement.　©　2016　IOS　Press　and　the　authors.