Abstract: To investigate the contribution of valine to cigarette smoke components, stable isotope-labeled valine was added into cut tobacco, and qualitative and dose-effect relationships between valine and cigarette smoke components were studied by analyzing the particulate and vapor phase components in mainstream cigarette smoke with GC/MS. The results showed that:1) Valine participated in the formation of 2-methypropanal, 3-methylbutyric acid, methylpyrazine, isobutane, 2-methyl-1-propylene and 2-cyclopenten-1-one during smoke formation. 2) Tobacco valine contributed about 69% of 2-methypropanal in the smoke, and its contribution rate to the other five compounds were less than 5%. The olfactory effect of valine on cigarette smoke was mainly due to the increase of 2-methypropanal in smoke. 3) All carbon atoms in the formed 2-methypropanal structure originated from valine.