A cold-launch method, comprising providing a cold-launch device, the cold-launch device comprising a high-energy gas resource, a gas cylinder, a control valve, multiple pistons, a gas-liquid mixing cylinder, and a shuttle vehicle for carrying an aircraft, wherein said high-energy gas resource is connected to said gas cylinder whereby supplying a high-energy gas thereto; enabling said high-energy gas in said gas cylinder to enter said gas-liquid mixing cylinder via said control valve; pushing all of said multiple pistons and said shuttle vehicle; and launching the aircraft at a constant power; wherein the cold-launch device further comprises a launching energy recovery device comprising a buffer spring, an energy recovery pump, a lifting cylinder, a sensor, a stop cylinder, and a guide rail; wherein said energy recovery pump and said lifting cylinder are disposed on said shuttle vehicle; said shuttle vehicle is disposed on said guide rail; and said sensor and said stop cylinder are disposed in the front of said guide rail; said gas-liquid mixing cylinder comprises a first cavity and a second cavity; said multiple pistons are sequentially connected to one another and are disposed in said second cavity of said gas-liquid mixing cylinder; an oil outlet is disposed on a wall of each of said multiple pistons except for the last of said multiple pistons; hydraulic oil is disposed in said second cavity; the last of said multiple pistons is connected to said shuttle vehicle; and the step of pushing all of said multiple pistons and said shuttle vehicle is performed by enabling said high-energy gas to push said first of said multiple pistons, enabling said hydraulic oil to flow in said second cavity via said oil outlet to sequentially push said multiple pistons, and enabling the last of said multiple pistons to push said shuttle vehicle; and the step of launching the aircraft at a constant power is performed by unloading said gas-liquid cylinder by means of said control valve and resetting said shuttle vehicle by said buffer spring. providing a cold-launch device, the cold-launch device comprising a high-energy gas resource, a gas cylinder, a control valve, multiple pistons, a gas-liquid mixing cylinder, and a shuttle vehicle for carrying an aircraft, wherein said high-energy gas resource is connected to said gas cylinder whereby supplying a high-energy gas thereto; enabling said high-energy gas in said gas cylinder to enter said gas-liquid mixing cylinder via said control valve; pushing all of said multiple pistons and said shuttle vehicle; and launching the aircraft at a constant power; wherein the cold-launch device further comprises a launching energy recovery device comprising a buffer spring, an energy recovery pump, a lifting cylinder, a sensor, a stop cylinder, and a guide rail; wherein said energy recovery pump and said lifting cylinder are disposed on said shuttle vehicle; said shuttle vehicle is disposed on said guide rail; and said sensor and said stop cylinder are disposed in the front of said guide rail; said gas-liquid mixing cylinder comprises a first cavity and a second cavity; said multiple pistons are sequentially connected to one another and are disposed in said second cavity of said gas-liquid mixing cylinder; an oil outlet is disposed on a wall of each of said multiple pistons except for the last of said multiple pistons; hydraulic oil is disposed in said second cavity; the last of said multiple pistons is connected to said shuttle vehicle; and the step of pushing all of said multiple pistons and said shuttle vehicle is performed by enabling said high-energy gas to push said first of said multiple pistons, enabling said hydraulic oil to flow in said second cavity via said oil outlet to sequentially push said multiple pistons, and enabling the last of said multiple pistons to push said shuttle vehicle; and the step of launching the aircraft at a constant power is performed by unloading said gas-liquid cylinder by means of said control valve and resetting said shuttle vehicle by said buffer spring.