The invention provides a fusion method and a fusion system for a spacecraft power supply and distribution big image and energy simulation data. The method comprises the steps of: acquiring variations of driving parameters of entity objects in the power supply and distribution big image in real time, sending the variations of the driving parameters to an energy simulation model library to carry out energy simulation, and generating the energy simulation data, wherein the driving parameters of the entity objects comprise an electrical characteristic variable, a driving parameter of a dynamic component, a driving parameter of a simulation animation flight orbit and a driving parameter of a key curve; and receiving the energy simulation data in real time and matching the energy simulation data into the power supply and distribution big image to carry out display output. According to the fusion method and the fusion system which are provided by the invention, by establishing the energy simulation model library matched and related with the driving parameters of the entity objects in the spacecraft power supply and distribution big image, acquiring the simulation data according to a single-step solution step length, carrying out automatic fusion, distinguishing and regulation and attaching the simulation data to display objects of the power supply and distribution big image, information fusion of the spacecraft power supply and distribution big image and the energy simulation data is implemented, and digital modeling, simulation, analysis and verification are implemented.