In order to investigate the reduction of free radical and tobacco-specific nitrosamines (TSNAs) by tea filter, the content of free radical in cigarette mainstream smoke was detected by electron spin resonance (ESR) spectroscopy in conjunction with the spin trapping method. The experimental results showed that the contents of free radical in gas phase and solid phase of tea filter cigarette mainstream smoke were reduced by 16.42%~0.48% and 12.36%~16.48%, respectively, compare with regular filter cigarette. The tobacco-specific nitrosamines (TSNAs) were detected by gas chromatography-thermal energy analyzer. The results indicated that the contents of NNN, NAT, NAB, NNK and total TSNAs in tea filter flue-cured cigarette mainstream smoke were to be reduced by 16.88%, 15.12%, 26.04%, 11.39% and 14.61% respectively, the contents of NNN、NAT、NAB、NNK and total TSNAs in tea filter blended cigarette mainstream smoke were to be reduced by 23.04%, 11.62%, 17.41%, 17.38% and 17.41% respectively, compare with regular filter cigarette. So application of tea-filter in cigarette is an effective way to reduce harmful components in cigarette smoke.