In order to study the deformation law and failure mode of overburden rock in the process of mining, taking No.4314 Face of Chengzhuang Mine as the research object, the 'two zones' monitoring system was constructed by using distributed optical fiber sensing technology. Firstly, the strain calibration test of 5 mm steel strand fiber was carried out by drawing test device, and the strain-frequency shift coefficient of 5 mm fiber was 0.049 54 MHz/με. Then through the on-site monitoring research, the monitoring of the deformation of the overburden rock of the working face and the determination of the height of the 'two zones' were realized. The results showed that the strain variation characteristics of the optical fiber in the caving zone and the fracture zone were similar. The strain was first generated at the bottom of the hole, and then gradually developed to the orifice position. The development heights of caving zone and fractured zone of No.3 coal seam were determined to be 16.7 m and 63.6 m respectively, which were verified by theoretical calculation and numerical simulation. The research results showed that it was feasible to monitor the ' two zones ' on the overburden rock of the working face by using distributed optical fiber technology.