The invention discloses a flood inundation analysis and early warning system for power transmission facilities. The system is composed of a flood inundation analysis module, a data presentation module, a flood inundation statistic output module, a power transmission facility inundation knowledge base module and a early warning module, can quickly, accurately and scientifically simulate, measure and calculate the flood inundation range around the power transmission facilities and the water depth distribution of the inundated area, and can respectively present the analysis result in two-dimensional and three-dimensional views so as to report the inundation state of the power transmission facilities and early warn the inundation risk of the power transmission facilities, thereby providing important information support and decision basis for flood prevention and disaster mitigation for the power transmission facilities.