This　paper　introduces　the　digital　light　processing　(DLP)　technology　as　the　main　principle　of　3D　printing　technology　and　discusses　issues　on　optical　system　in　detail.　This　existing　3D　printing　technology,　the　principle　of　stereolithography　technology　and　DLP　technology　were　introduced.　Introduced　with　DLP　technology　as　the　core　of　3D　printing　technology,　including　the　basic　structure　of　the　system,　and　how　DLP　technology　used　in　rapid　prototyping　were　explained.　And　the　digital　micro-mirror　device　(DMD)　composition　and　the　driving　principle,　the　typical　structure　of　an　optical　system　used　in　DLP　technology,　as　well　as　their　effects　on　3D　printing　technology　were　interpreted.　Then,　the　3D　printing　applications,　and　the　problem　of　DLP　technology　such　as　the　suitable　DLP　optical　system　wavelength,　the　projection　format　uniformity,　and　molding　accuracy　were　discussed.　Finally,　the　advantages　and　disadvantages　and　disadvantages　of　DLP　technology　in　the　field　of　3D　printing　were　summanized.　©　2015,　Beijing　University　of　Technology.　All　right　reserved.