During the season when the river water freezes or the river ice melts, ice flood disaster usually occurs in Ningxia-Inner Mongolia section of the Yellow River valley. Based on the meteorological and hydrological observations and NCEP/NCAR 6h analysis dataset of 1°×1°, the characteristics and causes of the disaster are analyzed by thermodynamic and dynamic methods. The results indicate that the disaster occurs under some meteorological, geographical and hydrological conditions. The freeze-up/break-up is related closely to the cold/warm air incursion and abrupt decreasing/increasing of temperature under advantageous large-scale circulation. The temperature advection and diabatic factor have an effect on the temperature change, while the intensity of the cold/warm air depends on the vorticity advection.