Abstract: A battery pack leakage detection system and detection method are provided. The system includes a test container, a gas filling subsystem, a gas stirring subsystem and a test analysis subsystem. The method can test the sealing performance of the battery pack under the atmospheric pressure, so that the battery pack can meet the corresponding sealing grade requirements of IP67 and IP68. The method not only solves the problem that the traditional gas detection method cannot meet the test requirements of IP67 and IP68 due to insufficient measurement precision, but also solves the problem that the traditional vacuum helium detection method will damage the battery cells in the battery pack.