Abstract: Disclosed is a particle algorithm-based method for underwater detection and operation positioning of a reservoir dam system. A water body is stimulated by adopting a smoothed particle hydrodynamics (SPH) method, the ROV is simulated by adopting a discrete element method (DEM) unit formed by a series of particles, an umbilical cable between the ROV and a water surface control unit are simulated by a spring unit, dynamic interaction among the ROV, water flow and the cable are calculated by combining the SPH method and the DEM, and real-time motion positions of the ROV and the cable in complex environments are calculated and obtained; and a relative position between the ROV and the surface control unit can be calculated through the real-time position of the cable, and the real-time underwater positioning of the ROV is realized in combination with an absolute coordinate position of the surface control unit.