Given that the settings of low exciting limiter of automatic voltage regulator and of loss-of-excitation protection cannot be established in a same coordinate and therefore cannot cooperate very well， a practical protection setting method is proposed. First， three low exciting limit curves corresponding to the changes of generator terminal voltage are analyzed. Then， according to the electric theory， the mapping relationship and equation between the low exciting limit curve and loss-of-excitation protection impedance circle are established. On this basis， the methods of how to match the protection settings， how to verify and how to apply in the real projects are proposed. Finally， a detailed example of calculation procedure is presented.