A novel fiber Bragg grating thermal tuning scheme is proposed, theoretically analyzed and experimentally studied. The device made from this scheme is named doubleshoulder beam (DSB). Experimental results demonstrate that DSB is an effective thermal tuning technique. A thermal sensitivity of 0436?nm/℃, 50 times that of the bare fiber grating, is experimentally achieved. To our knowledge, this is the largest thermal sensitivity ever demonstrated. The repeatability and lin earity of the technique is very well. The most important advantage of DSB, as a breakthrough to conventional thermal tuning technique, is its great flexibility. It makes the thermaltuning efficiency of fiber grating no longer limited by the thermalexpansion coefficient of the drive materials, but can be designed according to practical requirements. This technique is expected to have a vast application in fields such as laser tuning, high sensitivity temperature sensing, sensor demultiplexing and so forth.