The invention provides a gas pipeline leak detection and alarm device with the emergency cut-off function. The gas pipeline leak detection and alarm device with the emergency cut-off function comprises a detachable pipe body, a movable sealing ball core, a detection sensor, an adjustable resistance spring, a gas flow regulation pipe, a sound and light alarm module and the like. The gas pipeline leak detection and alarm device with the emergency cut-off function is perpendicularly installed on a user gas pipeline, and by utilizing the principle that gas flow is generated because of differentialpressure formed in the pipeline under the situation of leakage during gas using, the light movable sealing ball core in the device is enabled to suspend in air, and then triggers the sound and lightalarm module to give out an alarm signal; under the situation that gas is overused or gas leaks out after the pipeline disconnects, the movable sealing ball core is stressed with thrust of gas flow below and quickly moves upwards till the movable sealing ball core completely seals a gas outlet to stop leakage, and the emergency cut-off function for safety is achieved; and after a user stops usinggas appliances such as a kitchen range and a water heater, the user gas pipeline automatically goes into the protection state for 24-hour leakage detection and alarm. The gas pipeline leak detection and alarm device with the emergency cut-off function has the advantages of being simple in structure, low in cost, high in safety, and capable of adapting to various places needing gas.