FBG strain sensing technology is used to dynamically detect tread wear of railway train wheels. Dozens of FBG track strain sensors are installed as lines along railway tracks in crosstie sections. Train wheels one by one roll on the track and load the sensors, groups of strain peak are taken. The strain curve of defective wheel appears a gap or with serration. By means of strain pulse processing program, tread wear and wheel health condition are obtained. FBG strain gauge is employed to increase the measuring sensitivity. Protecting methods for sensors and fiber are adopted to keep them surviving from harsh application environment. The examples of detecting results are given to show the validity of this FBG application.