Abstract: The mainstream smoke constituents retained by Cambridge filter pad and cigarette filter were analyzed puff by puff under the standard smoking regime,and the change of total particulate matter filtration efficiency(TPMFE),nicotine filtration efficiency(NFE) and tar filtration efficiency(TFE) was studied.The results showed that:1) the filtration efficiency differed from puff to puff;2) TPMFE and TFE increased,while NFE decreased puff after puff,their order was TPMFE >TFE >NFE at the end of smoking;3) when the filter length increased from 20 mm to 30 mm,the order of TPMFE and TFE changed from TFE>TPMFE to TPMFE>TFE during first puffing,while the change trends of TPMFE,TFE and NFE did not affected by filter length during the whole process of smoking.