To provide a power generating method and system capable of performing high efficiency power generation both in instantaneous power and integration power without causing cost increase.

The power generating system comprises an MHD generator 6 equipped with a power generation channel 3 arranged at the in-furnace gas channel in waste heat treatment equipment in order to fluidize conductive fluid, an electromagnet 5 generating a magnetic field intersecting the power generation channel 3 perpendicularly, and an electrode for taking out a current generated when the conductive fluid flows through the power generation channel 3, and a unit 7 for adding a conductive substance coming from the waste and/or gas containing oxygen to the in-furnace gas flowing through the power generation channel 3.