Abstract: In order to investigate the pyrolytic products of polysaccharide from Gracilaria lemaneiformis and the effects of its application on the deliveries of harmful components in mainstream cigarette smoke,the pyrolysis of polysaccharides was carried out under the conditions simulating cigarette smoking and the pyrolytic products were determined by GC/MS,meanwhile,the deliveries of seven harmful components,including CO,HCN, NNK,NH₃,BaP, phenol and crotonaldehyde, in mainstream smoke of the cigarette containing the polysaccharides were analyzed. The results showed that within the selected temperature ranges of 300,600 and 900℃,the kinds and total amount of pyrolytic products increased with the rise of pyrolysis temperature. The major pyrolytic products were furans,ketones and organic acids,and total amount of furans accounted for nearly 30%. The application of polysaccharides from Gracilaria lemaneiformis had no significant impact on the deliveries of harmful components in mainstream cigarette smoke.