The invention discloses a method for simultaneously testing oscillating microwave signal frequency and power of a backward wave tube. The method includes the following steps that 1, the backward wavetube is placed into a vacuum oven to eliminate air and obtain A; 2, leads are tin-soldered on output electrodes of the A and different output electrodes of the backward wave tube are differentiated bylead color marks with different colors to obtain B; 3, the ceramic part of an electron gun of the B is evenly coated with silicone rubber and placed for no less than 24 hours, then the encapsulationof insulating silicone rubber is conducted, and then the ceramic part of the electron gun is placed for no less than 12 hours to obtain C; and 4, a fixing supporting frame of a magnetic system is mounted at the C to obtain D1, the D1 is installed in the magnetic system to obtain D2, the D2 is disposed on a three-axial-direction adjusting tool, and the connection part is fixed to obtain D. The method can simultaneously test oscillation frequency and power in the working process of the backward wave tube.