For short circuit fault analysis on double-circuit transmission line， a method based on three sequences is put forward. Combining with the boundary conditions of fault， a new approach for calculating the faulty electric quantities is presented， and the interconnections of sequence networks of typical fault types are given. Because it keeps the independence of the two lines， it can serve as a basic theoretical approach for studying the process of fault inception， tripping and reclosing on double-circuit transmission lines with some special line construction modes such as different line parameters or voltage classes of the two circuits on the same tower.