The invention discloses a TE<0>0n / TE<0>1n mode exciter. In the TE<0>0n / TE<0>1n mode exciter, one end of a first rectangular waveguide (1-2) is connected with an input port (1-1), one end of the first rectangular waveguide (1-2) is connected with a first first-order matching step waveguide (1-3), one end of a second rectangular waveguide (1-4) is connected with the first first-order matching step waveguide (1-3), one end of the second rectangular waveguide (1-4) is connected with a second first-order matching step waveguide (1-5), a short-circuit surface is arranged at the other end of the second first-order matching step waveguide (1-5), one end of a third rectangular waveguide (1-8) is connected with the side wall of the second rectangular waveguide (1-4) through a coupling hole (1-7), one end of the third rectangular waveguide (1-8) is connected with a third first-order matching step waveguide (2-2), one end of a first round waveguide (2-5) is connected with the third first-order matching step waveguide (2-2), one end of the first round waveguide (2-5) is connected with a gradually-charging round waveguide (2-6), one end of the second round waveguide (2-7) is connected with the gradually-charging round waveguide (2-6), one end of the second round waveguide (2-7) is connected with an output port (2-1), and symmetric ridges with different sizes are arranged on the inner wall of the first round waveguide (2-5). The TE<0>0n / TE<0>1n mode exciter has the advantages of low reflection, high mode purity, and relatively wide working bandwidth.