EPRI-E' equivalent law was adopted to model the simulation system which includes ultra-high voltage system and high voltage distribution network. The influence on the security and stability of receiving-end grid with the operation of UHV was analyzed under three situations, including UHV fault, internal line fault and the main power plant fault of the distribution network. And then, this paper defined the shortest path to determine the affected area. The research has shown that, if double lines of UHV system jump after line fault, the flow of the outlets of 220 kV site with 5 of the shortest path becomes larger, and some lines will even overload and cascading failure may be caused. The risk of system collapse increases if the internal line or the main plant fault and UHV fault occur simultaneously. Finally, according to the operation characteristics of UHV, this paper proposed the corresponding stability control measures to ensure the normal operation of the power grid.