Reduction of tobacco specific nitrosamines (TSNAs) in tobacco and cigarette smoke is a research hotspot. The systematic technologies for reducing TSNAs in both agricultural and industrial areas were developed and applied. The TSNA levels for the upper and middle leaves of Burley tobacco could be reduced by 23.0 % and 23.9 %, respectively, by the foliage spray of purslane extract during tobacco cultivation. Through breeding improvement of Maryland tobacco Wufeng 1# to reduce nicotine conversion rate, TSNA levels for the upper and middle leaves of Maryland tobacco could be reduced by 66.3 % and 70.1 %, respectively. By spraying 4.5 % (W/W) of purslane extract and 0.4 (W/W) nanometer silica dispersion liquid during threshing and redrying, the TSNA level of tobacco could be reduced by 36.0 % and 20.5 %, respectively, compared with that of the control. During tobacco storage, the TSNA level of tobacco using vacuum packaging could be 45.98 % lower than using ordinary packaging and the TSNA level of Burley and Maryland tobacco stored at 20 °C could be 49.5 % and 49.6 % lower than that of the tobacco stored at ambient temperature. The level of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in the cigarette smoke could be selectively reduced by 34.6 % when 5 % (W/W) of cytochrome P450 recombinase was added to Burley tobacco during processing. Using 10 % of reconstituted tobacco processed with 10 % (W/W) of nanometer silica and 4 % of cytochrome P450 recombinase could result in a 20.0 % decrease of TSNAs in cigarette smoke. The TSNA level in cigarette smoke could be reduced by 24.1 % by using complex cigarette filter containing 0.6 mg of modified nanometer silica and 16.8 mg of macroporous silica gel instead of cellulose acetate filter with the similar parameters. All the above TSNA reduction technologies combined and applied in cigarette manufacture could approach a selective reduction of 58 % of TSNAs in cigarette smoke and a 45 % decrease of the cigarette hazard index.