The technology of temperature measurement by distributed optic fiber is introduced in this paper. By laboratory tests and field tests, comparison and selection of distributed temperature measurement optic fiber, analysis of its accuracy and stability, monitoring and analyzing leakage in the embankment dam using distributed optic fiber, comparing with conventional monitoring technology, and it’s engineering applications are carried out. Based on these tests, the feasibility of and applicability to the monitor of the leakage in the embankment dam using distributed optic fiber are discussed. The technology of temperature measurement by distributed Raman optic fiber, whose sensitivity of temperature is ±0.5 ℃, is feasible in monitoring leakage in the embankment dam using temperature gradient analysis method and heating method. Comparing with the results measured by conventional monitoring technology, the accuracy of data measured by distributed Raman optic fiber and its reliability of monitoring leakage in the embankment dam have been verified. Monitoring leakage in the embankment dam using distributed optic fiber has obvious advantages, such as distributedness, long range and anti-interference.