With the impact of grid structure, generators distribution, generator units parameters, and load type, the system’s frequency characteristics presents temporal and spatial distribution. However, system frequency is the reference for formulating the UFLS scheme, which makes the action of UFLS device unsatisfactory. Based on the grid splitting in some region, this paper analyzes the dynamic characteristics of system frequency and the action of UFLS device in detail under the power shortage. Considering the impact factors such as frequency recovery effect, load shedding values and its types, etc., it studies the influence of load characteristics on frequency and proposes two research programs including decentralized load shedding and centralized cutting industrial load of large consumer. The research results show that cutting industrial load of large user can quickly restore the system frequency and have smaller influence on the residents’ load, therefore it has significant reference value on control strategy of frequency recovery in the grid operation and making the program of the UFLS.