Abstract: In order to master the dynamic height and developing law of the Water Conducting Fractured Zone(WCFZ) caused by the coal mining in large depth and thickness, the Brillouin optical time domain reflector(B OTDR) is applied to the field predicting. Taking the 150313 working face of Yinying Coal Mine as the background, with the detailed introduction of BOTDR and the theoretical analysis of the specific geological and productive conditions of the working face, the studies were carried out about the layout of the optical fiber(OF), the occurrence optimization of layout boreholes, the temporary safety measures and the characteristics of strain distribution. The test results showed that the optical fiber strain(1) appears strain peak distribution in the stratum with Lower strength and plateau distribution in the stratum with higher strength, (2) presents three stages:the initial platform stage, fast stretching stage and the final slow lifting stable stage in a single stratum, (3) characterize the height of WCFZ increases gradually with non-uniformity and non-linearity, and tends to be stable at last. The field test results are consistent with the theoretical calculation values and the previous similar model simulation test results, which shows that the BOTDR strain test method proposed in this paper is effective and feasible, and has certain practical and universal significance for popularizing the BOTDR monitoring of the WCFZ in coal mines and other similar underground structures.