The present invention provides a high expansion foam fire-extinguishing system including: an emission nozzle (9) to which a foam solution (Wg) prepared by mixing water (W) with a foam concentrate (16) containing a surface active agent (18) is sent under pressure; a flow passage (2); and a foam screen (7) upon which the foam solution discharged from the emission nozzle impinges, in which the foam concentrate used is one of one in which a mixing ratio of the foam concentrate with respect to the foam solution is an adjusted mixing ratio higher than a standard mixing ratio and one in which a content rate of the surface active agent with respect to the foam concentrate is a design content rate that is higher than a standard content rate, and in which a mixing ratio of the surface active agent is a concentration for design foam expansion ratio.