In engineering structures, it is a new approach to evaluate the structural health situation by use of optic fiber sensor. In this paper, a standard specimen beam, 200mm×300mm×3000mm, is chosen and the comparative experiment is executed for strain testing by FBG sensors and vibrating wire sensors which were widely used in bridge health monitoring. Experimental results show that the FBG sensors have a higher measurement precision, higher linearity and better noise resistance. Then we use traditional electrical resistance strain gage to calibrate the FBG sensors and obtain the strain degree of sensitivity, and apply them into bridge strengthening in the Wuhuang Highway in order to collect the strains of reinforcement bar in the deck pavement and the beams before and after the bridge strengthening. The above work is also to evaluate the effects of strengthening projects and carry out long-term structural health monitoring. The monitoring results show that the safety condition can be monitored conveniently with the FBG sensors testing system whose durability and stability can satisfy the need of bridge health monitoring. Finally, we also discuss the key problems and practical approaches in structural health monitoring process by use of embedded FBG sensors.