The invention provides a fire-fighting medium supply device and method for a substation fire-fighting robot. The fire-fighting medium supply device comprises a bearing mechanism, wherein a water supply mechanism, a foam supply mechanism and a water hose docking mechanism are borne on the bearing mechanism; the water supply mechanism comprises at least one fire-fighting water storage tank; the fire-fighting water storage tank is connected with a booster pump through a pipeline to provide pressure for water supply; a drain pipe of the booster pump is connected with a water hose through a joint;the foam supply mechanism comprises at least one foam storage tank; the foam storage tank is connected with a foam pump through a pipeline; a drain pipe of the foam pump is connected with a water inlet pipe of the booster pump; the water hose docking mechanism comprises a quick-plug joint arranged at the end part of the water hose and a supporting seat arranged on the bearing mechanism; a plurality of columns distributed circumferentially are arranged on the supporting seat; the water hose can be accommodated in the center of each column; two oppositely arranged pressing plates are arranged atthe end part of each column; the pressing plates can rotate relatively; and the quick-plug joint is movably clamped in the inner edge of each pressing plate.