Based on the ray theory of fiber grating diffraction,the sensing principle of fiber Bragg grating(FBG) was introduced.In consideration of the strain detection in practice of large scale equipments,expatiated on the principle and solution about temperature and strain cross sensitivity of FBG.Then the actuality of FBG packaging techniques in strain detection were summarized.The problems in existence and the developing direction of packaging techniques were pointed out.Finally,the way of calibration on FBG sensor and some notice was briefly introduced.