Abstract: When the conventional beam deposition method is applied to the internal beam parameters measurement in cyclotron, the induced radioactive contamination generated in the measuring probe will lead to unnecessary radiation hazards to the accelerator beam tuning staff. The AGM-6 gamma monitor was applied to on-line measurement of the induced radioactivity. By measuring the air kerma rate of the probe irradiated at different radii, the strength and the hazards of induced radioactivity were reflected indirectly. The results show that the high-frequency duty cycle should be reduced, and the probe should be cooled for 2-3 h before being removed in the beam tuning experiment. Otherwise, one should consider hazards of the residual induced radioactivity after the measuring probe being irradiated.