Abstract: Blister appeared on the surface of TP2 copper tube and the casting was studied by means of optical microscopy and SEM and EDS instrument. The results showed that Cu2O granules existed in TP2 copper cast ingot and extruding tube. During anneal processing in the reductive atmosphere, the air came from reductive reaction letted out to form bubbles on the tube surface.The measures to reduce the blister were discussed.