Abstract: For determining the airtightness of cigarette packets accurately,a negative pressure air extraction method was studied,the key test parameters were determined and the method was verified.The airtightness of packets of major domestic cigarette brands was detected by this method.The results showed that:1) The appropriate detection conditions were air extraction volume 200 mL/min,packet perforation depth>half of packet thickness.2) The coefficient of variation of detection results was less than 1%,it indicated that the repeatability of this method was good.3) The average airtightness of hard packets(-3.508 kPa) was better than that of soft ones(-1.138 kPa),and airtightness differed greatly between the hard and soft packets of different brands.The proportion of packets whose air tightness was better than the average level reached 60% for hard packets,while which was only 33.33% for soft packets.