Abstarct: Under frequency load shedding is one of the most important safety systems in order to maintain the stability of power systems against power shortage caused by severe disturbances. Today, due to the presence of distributed resources in many small networks, the maintenance frequency, especially when the demand of production is more important has found. To improve the traditional load shedding, frequency slope of the many attempts to use an indicator to determine the power deficit in the power system. Simultaneous use of the rate of change of frequency with time a frequency measurement system frequency load shedding ways to significantly increase their effectiveness in determining the exact amount of the deficit and improved the frequency profile. This research presents the ways in which they measure continuous measurement frequency and the average rate of change of frequency, the optimal amount of time to fix the frequency of the system is disconnected. Two examples of test systems simulation, implementation intentional islanding and Implementation of the proposed methods on them shows the effectiveness of the proposed methods to remove the optimal amount of time for stabilizing the system frequency. An important feature of these methods can be quickly optimal disconnected of load at the moment of disturbance and improve the system frequency response curve the similar techniques mentioned.