In flood season, the formation of local floating pipeline occurs in river-network areas because gas pipeline is out of touch with riverbed. Under the combined effects of dynamic water, buoyancy, gravity and resistance of bank soil, pipeline generally presents three-dimensional bending. Applied is the infinite software CAESAR II to conduct numerical simulation of pipeline in order to obtain the stress distribution of local floating pipeline and establish mechanical model of pipeline under the action of water flowing. Taken are practical engineering examples of pipeline for specific analysis and obtained are stress distribution and deformation of pipeline and locations of dangerous points. Mechanical behavior of floating pipeline is influenced by many factors and analysis on change law of max pipeline equivalent stress has very important reference meaning for daily maintenance of gas pipelines in river-network area and making emergency plans.