Abstract: The present invention discloses an electrical state quantity prediction method and system and a control method and system for a UPS system. In terms of UPS system control strategies, relationships between predicted values of dynamic variables of the UPS system and switch variables of switch tubes are first obtained through a discrete model of the UPS system, then a target optimization control function is constructed based on MPC (Model Predictive Control), and finally, optimal switch variables at each time are obtained by traversing cost values Q of the target optimization control function in various switch states. The method of the present invention solves problems of complex cooperative control, difficult control optimization and the like in a multi-converter system, and improves work efficiency of a high-power UPS system and stability of the control system.