This paper analyzes some major factors for the impact of wind power integration on power system dynamic frequency characteristics in theory. Combining with an actual grid, test scenarios with various scales of doubly fed induction generator (DFIG)-based wind power integration are formulated. Through simulation in the scenarios with FASTEST software, the impacts on the action of under frequency load shedding (UFLS) scheme are displayed in two aspects, the rate of change of frequency (ROCOF) and wind turbine generator own protection. Simulation result shows that the ROCOF will not affect the lock action of UFLS devices in the test system of this paper. Wind turbine generator protection may worsen frequency responses, so it is proposed to be in harmony with the design of UFLS scheme.