Based on the general law of system frequency variation characteristics in low-frequency emergency state，frequency influencing factors in a small weak receiving power grid are analyzed at length during the disturbance due to power shortage，such as the quantity of power shortage，number of operating units，type of load，fault locations and types，load shedding time，load shedding ratio，whether to switch the capacitor or not etc.Then the theoretical derivation is qualitatively given.On the basis of analysis of the influencing factors in the above-mentioned small isolated power grid，in light of the characteristics of the excessively large dive depth and long duration of the frequency first swing，two coordination schemes of load shedding and under-frequency load shedding are proposed:load shedding time and load shedding ratio coordination and device outlets coordination.Take a real small weak receiving power grid in Northwest China as an example.Simulation results have verified the rationality of the coordination principle proposed and the feasibility of the two coordination schemes.