The invention discloses an ash blowing method for an ash blowing device of a full-telescopic type gas-gas heater (GGH) and the ash blowing device, wherein the method comprises the following steps of: dividing a rotor of the GGH into ring-shaped blowing sections along with the radial direction of the rotor of the GGH, wherein each blowing section comprises at least one of blowing journeys along with the radial direction, and each blowing journey is the step diameter of the ash blowing device; respectively setting the blowing time of each blowing journey for each blowing section; and blowing each blowing section according to the blowing time. According to the invention, the blowing process can be controlled according to the blowing time required by different blowing sections, the high-efficiency blowing can be realized by setting the blowing time according to the scaling properties of the different blowing sections, and the damage to the GGH caused by blowing can be reduced into minimum.