To solve the cross-sensitivity to temperature of fiber Bragg grating (FBG) strain sensor, an effective method is firstly proposed for the discrimination of strain and temperature by using a single FBG adopting a special compensated structure, which is based on the thermal stress. The relationship of strain and temperature responses of FBG is analyzed theoretically. The experimental results are in agreement with the obtained theoretical analyses. This sensor structure has excellent characteristics, such as simple structure, easy manufacture and higher strain sensitivity.