Abstract: The design of permanent magnet packaging for a compact S-band 8-cavity all-cavity axial extraction relativistic magnetron (R8 ACAE-RM) with an output mode of TE₁₁ is preliminarily explored. The inner magnetic block is placed at both ends of the anode block in the anode cylinder, and the outer magnetic block is placed outside the RM, which generates a magnetic field of about 0.34 T and a length of 72 mm on the axial uniform zone in the interaction zone, and the weight of the permanent magnet is only 21 kg. Compared with the traditional external magnet system, this design can reduce the weight of the magnet, the magnetic field strength in the interaction zone is more uniform, and the system structure is more compact, which can meet the lightweight and miniaturization requirements of high-power microwave source systems. The device applies π mode as its operating mode, four 90° sector TE₁₁ modes are extracted through all-cavity axial extraction structure, and a coaxial-plate-inserted mode converter is designed for mode conversion, thus to obtain TE₁₁ mode in circular waveguide. In particle-in-cell (PIC) simulation, the proposed R8 ACAE-RM can generate a microwave power of 1.06 GW with a pure TE₁₁ mode at the frequency of 2.44 GHz under the conditions of a guiding magnetic generated by the inner and outer magnetic blocks, a diode voltage of 320 kV, and power conversion efficiency of 47%.