Solar　light　pipe　combined　with　photocatalysis　could　introduce　sunlight　into　rooms　and　also　has　air　purification　function.　The　length　of　the　solar　light　pipe　is　0.55　m　with　a　diameter　of　0.28　m.　The　average　ratio　of　reflection　of　the　surface　of　solar　light　pipe　is　0.82.　Snow　shaped　astigmatism　board　has　a　diameter　of　0.28　m.　Coating　DegussaP25　solution　evenly　on　the　rugged　side　for　the　quality　of　1.75　g.　The　experiments　show　that　when　the　coating　side　away　from　the　sun　the　lighting　degree　may　be　reduced　compared　with　when　facing　the　sun.　But　the　average　reduction　was　only　3.03　percent　which　would　not　have　a　significant　impact　on　indoor　lighting.　The　experiments　also　show　that　in　a　sunny　summer　morning　under　the　direct　sun,　Solar　light　pipe　combined　with　photocatalysis　could　reduce　formaldehyde　in　a　little　box　of　0.1　m3　volume　from　1.010-6　to　0.1910-6.　Under　the　direct　noon　sun　within　1h　formaldehyde　volume　from　1.010-6　down　to　0.1710-6　with　faster　and　more　complete　degradation　of　formaldehyde.　In　direct　afternoon　sun　within　1　hour,　the　volume　fraction　of　formaldehyde　reduced　from　1.010-6　down　to　0.210-6.　The　rate　of　degradation　in　the　afternoon　was　slower　than　that　in　the　morning　and　noon,　but　also　achieved　a　good　performance.