The invention discloses a double-bus line protection method and device of integrating voltage switching. The bus voltage of double buses directly enters a protection device sampling circuit; meanwhile, the position of a line knife switch is switched into the protection device as a switch-in quantity; an auxiliary contact of using the line knife switch directly enters the protection device for judgment of voltage switching; the protection device selects the bus voltage through logic judgment according to the position of the knife switch; and when the auxiliary contact of using the line knife switch is abnormal, the bus voltage can be selected by adopting a manually strong setting method. Through the design mode, the problem that false coordination can exist in the bus voltage is thoroughly solved; a special voltage switching device is omitted in line protection; the investment is reduced; meanwhile, connection of the protection device is simplified; and the reliability of the protection device is improved.