The invention discloses a gas-liquid contact type non phase transition intermediate medium heat transfer wet desulfurization method and a device thereof. Flue gas enters a flue gas cooling section through an air preheater to carry out pre-desulfurization and release heat towards desulfurization liquid to bring down temperature, and then enters a desulfurization section; the desulfurization liquidabsorbs the heat of the flue gas to cause the temperature to rise to 90 to 95 DEG C and then enters a purified flue gas heating section and an air preheating section to release heat again; the lower part of the desulfurization section of the device is connected with the flue gas cooling section which is respectively connected with the purified flue gas heating section and the air preheating section; the air preheating section is connected with the air preheater and the air preheater is connected with the flue gas cooling section; an outlet at the top of the desulfurization section is connected with the purified flue gas heating section; the bottoms of the air preheating section and the purified flue gas heating section are connected with a sedimentation tank which is connected with a spray device at the upper part of the desulfurization section. The method and device greatly improve the heat efficiency of boilers; meanwhile, the minimum wall temperature of the air preheater is greatlyincreased and far away from a flue gas acid dew point, thereby guaranteeing the safe operation of boilers and preventing heating surfaces from acid dew corrosion.