The invention discloses a leakage detection system and method, relates to the technical field of detection equipment and aims to realize effective detection on hot water leakage of a shell-and-tube heater. The system comprises a shell-and-tube head exchanger taken as a detection object, wherein the shell-and-tube heat exchanger is connected with a detection pipeline communicated with a pipe casing, and the detection pipeline is provided with a liquid level detection mechanism used for detecting a liquid level. When water leaked from the pipe casing flows into the detection pipeline, different liquid level leakage indication signals can be fed back by the liquid level detection mechanism according to detected liquid level heights. The system is advantaged in that the structure is simple, the leakage detection and leakage liquid processing response speed is fast, severe economic loss and safety problems caused by entry of hot water into the pipe layer even downstream gas turbines can be effectively prevented, and production safety is guaranteed.