Constant development in mechanical engineering increasingly employs machines with high frequency revolutions requiring high efficiency and noiseless running and thus qualitative demands laid for belt gears increase as well. A new device for measuring and diagnostics of belt gears was designed to realize experimental measurements. Measurements can determine, for instance, slip of a V-belt expressed by the coefficient of elastic creep and of specific slip. Measurements regarding the designed device can be performed when input revolutions of the electric motor and torque of the belt gear are constant and tensioning force of the belt gear varies or when input revolutions of the electric motor and tensioning force are constant and output torque varies. The monitored parameters are assessed by particular software solutions.