Abstract <p>The effect of the electron relativistic beam (REB) current on the operation mode of a plasma relativistic microwave generator with inverse geometry (where a tubular REB is located around the plasma, not inside, as in earlier works with conventional geometry) and its radiation characteristics have been studied using the numerical simulation method (the PIC method). It is shown that an increase in the REB currents does not lead to an increase in the energy of the output microwave pulse of a plasma relativistic generator but to its decrease for a large range of plasma densities up to 7 × 10¹² cm^–3. When a certain threshold of the REB current is exceeded, the electron energy distribution function of REB changes its shape, the transverse plasma density profile degrades, an ion background is formed, and, as a consequence, shortening of the microwave pulse and a change in the generation mode occur.</p>