<p>We present the results of studying experimentally how axial misalignment of the cathode unit in a magnetron-injection gun affects the parameters of the helical electron beam and the efficiency of a two-resonator gyroklystron. The gyroamplifier uses an electron gun, whose design makes it possible to move the heated cathode. Four screws, which are located at an angle of 90° to each other, are used to move the cathode in a radial plane perpendicular to the axis of the system. The electron distribution functions in longitudinal velocities in the electron beams formed by different areas of the cathode are studied in an adjusted electron-optical system and at two values of the radial displacement of the cathode from the optimal position. It is shown that the pitch factor of the entire beam depends weakly on this displacement, while the spread of the longitudinal velocities increases sharply when the symmetry of the cathode unit is violated. The velocity spread increases due to the displacement of individual distribution functions of the electron beams emitted by different sections of the cathode into the regions of the longitudinal velocities, which are opposite to each other relative to their position in the adjusted electron-optical system. In addition, the increase in the spread is associated with the influence of the variable fields of the longitudinal low-frequency space charge oscillations, which are accumulated in the trap between the cathode and the magnetic mirror, on the passing beam. The main reason for the observed experimental drop in the efficiency with the increasing bias is determined by the spreading of the phase bunches of the grouped beam in the drift space, when the electrons arriving at the output cavity have significantly different longitudinal velocities due to a large velocity spread, which results in that some of them fall into non-optimal phases of the high-frequency field of the working cavity mode.</p>