The present application provides an energy-saving ventilation and air-conditioning system for a subway, comprising: a combined air-conditioner and a substation air-conditioner deployed in a ring-control room at the main end of equipment in a subway station, the combined air-conditioner being used for supplying air to a public area of the subway station to cool down the temperature, and the substation air-conditioner being used for supplying air to a room of a substation in the subway station to cool down the temperature;The system also includes: a connecting pipeline, a connecting air valve, and a control unit; one end of the connecting pipeline is connected to the exhaust air duct of the combined air conditioner, and the other end is connected to the air mixing box of the air conditioner at the power substation; the connecting air valve is provided in the connecting pipeline; the control unit is electrically connected to the connecting air valve and is capable of controlling the opening and closing opening of the connecting air valve to control the size of air volume and time period of introduction of air flow introduced into the air mixing box of the air conditioner at the power substation from the return air duct of the combined air conditioner. The air volume and the time of introduction are controlled. Hereby, it realizes the gradient recycling of energy, effectively reduces the operation energy consumption, the system control is simple, the new construction and renovation implementability is strong, and it has good economic benefits.