A battery pack and a liquid leakage detection method thereof are provided. The battery pack comprises a plurality of battery cells, a isolated liquid and a battery box containing the isolated liquid. The battery cells are soaked in the isolated liquid. The battery box comprising a box body and a cover plate. The isolated liquid is a fire-retardant and insulating liquid that has a specific gravity smaller than an electrolyte and is insoluble in the electrolyte. A collection portion is disposed at the bottom of the battery box, and a detection component is disposed in the collection portion. The present disclosure encloses the leaked electrolyte in the fire-retardant isolated liquid and uses the detection component to detect a resistance value of the isolated liquid so as to improve the safety of the box body.