Abstract: Based on our findings published in 2016, we have carried out further studies on the performance improvements of the relativistic magnetron using all-cavity output and semi-transparent cathode. By modifying the semi-transparent cathode, that is, rotating it in azimuthal direction and using uneven height of the electron emission surfaces, and partially optimizing of the cathode parameters, the mode competitions in the initial stage are prohibited effectively in relatively wider range of the operating parameters. At the same time, the starting up time is shortened and the output efficiency is improved obviously. After optimization, the three dimensional particle-in-cell simulations show that with the beam voltage of 518 kV and beam current of 4.1 kA, 1.42 GW output microwave with efficiency about 66% can be obtained at S-band. The corresponding applied magnetic field is 0.575 T. The effects of the beam voltage and applied magnetic field on the output characteristics are also obtained.