There exist a lot of veins in porphyry copper deposits, and their formationis thought to be genetically related to the alteration of deposits and particularlyto mineralization. By applying the theories of elastic mechanics, fluid mechanicsand fracture mechanics, the authors have constructed a dynamic model of veinformation in porphyry copper deposits; determined the vein's length, width,ratio of length to width, and temporal relationship between fluid pressure andvein extension as well as extensional rates of the vein in directions of its lengthand width; analyzed, in a concrete way, the morphological features of veins inporphyry copper deposits and the complex cross cutting relation between veins ofdifferent types; studied the intrinsic relations between the formation of veins andalteration and minenalization in deposits, and finally, pointed out the theoreticaland practical significance of this research.