The invention discloses a non-introducing magnetic field compact high-power microwave device, which comprises an anode, a cathode, a coaxial inner conductor, a coupling plate, and four annular metal grid meshes, wherein the anode is provided with an accommodating cavity; the cathode is connected with the anode via an insulator and is located in the accommodating cavity; the coaxial inner conductor is connected with the anode and is located in the accommodating cavity, and the coaxial inner conductor and the accommodating cavity form a coaxial structure; the coupling plate is connected onto the end surface of the coaxial inner conductor; the four annular metal grid meshes have the same circle center but different semidiameters; the metal grid meshes are fixedly connected onto a grid mesh supporting area and the coaxial inner conductor; and the four annular metal grid meshes, the coupling plate, and the coaxial inner conductor form a resonant cavity. An electron beam emission mode is changed into a radial direction, the metal grid meshes are used for separating the cavity; as the electron beam is radially emitted, the electron beam has a large cross section, and a higher beam current strength can be transmitted in a low current density condition; and due to the radial structure, the space charge effects are small, the current limit current is large, input of large beam current can be allowed, and virtual cathode effects are not generated.