The invention relates to a method for detecting the air tightness of 12 stations of an automotive water seal. In the method, leaked air bubbles are collected and are converted into differential pressure to enter a differential pressure transducer, and the differential pressure is converted into electric signals for detection, judgment and sorting. The device comprises airtight detection lower dies, airtight detection top dies, a leaked air collecting pipe, die pressing air cylinders, a machine frame, a micro-differential pressure transducer and a touching control screen, wherein a plurality of airtight detection lower dies which are arranged uniformly are arranged at the bottom of the machine frame; the die pressing air cylinders corresponding to the airtight detection lower dies one by one are arranged right above the airtight detection lower dies; the airtight detection top dies corresponding to the airtight detection lower dies are arranged on the lower part of the diepressing air cylinders; and the airtight detection top dies are connected with the micro-differential pressure transducer through the leaked air collecting pipe. In the method and the device, the micro-differential pressure transducer is adopted, the accuracy reaches 9.8 Pa, automatic feeding, automatic detection, automatic judgment, automatic sorting, programmable control and human-computer interface operation can be performed, and the aims of multiple stations, high accuracy, automatic sorting and the reduction of artificial misjudgment are fulfilled.