Seepage monitoring is an important element in geotechnical engineering. This article proposed a new integrated system for seepage monitoring composed of a fiber Bragg grating (FBG) sensing system and a water-heating cycling system. The boiler is used as the heating equipment in the integrated system. The heated water is distributed to each heating pipeline for cyclic heating through the water separator and water collector. The FBG temperature sensors are preburied in the heating pipeline to monitor the water temperature in real time. Recognizing the correlation between the temperature field and the seepage field, we proposed to fit coefficient ξv according to the cooling curve and used it as an index to identify the seepage state. We conducted this numerical simulation to analyze the heat transfer process of the heat source in the porous media. We carried out the calibration experiments of seepage velocity using the FBG-sensing heating system in the porous medium with four different gradations. Our results showed that the temperature gradient decreased over time, indicating that the primary way the heat source was transferred was through the convective heat transfer caused by the seepage. Therefore, the coefficient ξv could be used as the seepage identification index. On the basis of our calibration experiments, we obtained the fitting formulas of ξv and the seepage velocity in four kinds of porous mediums. The formulas can be used for the inversion of seepage velocity. The experimental results proved that ξv was unrelated to the initial cooling temperature. This finding showed that the influence of an uneven temperature distribution along the heating pipeline on monitoring results could be ignored.