Abstract: In order to investigate the releases of harmful components in mainstream aerosol of heat-not-burn tobacco products, the releases of harmful components (NFDPM, nicotine, CO, HCN, NNK, NNN, NH₃, BaP, phenol, crotonaldehyde, formaldehyde, acetaldehyde, acrolein, 1, 3-butadiene, and benzene), water, propylene glycol and glycerin in mainstream aerosol of 11 iQOS samples and 3 glo samples were tested under ISO and Health Canada Intense (HCI) puffing regimes. The results showed that:1) The total release of aerosols, mainly water (mass fraction 70%), from heat-not-burn products were much higher than those released from combustible cigarettes. 2) iQOS and glo released similar levels of NNK, NH₃ and crotonaldehyde as combustible cigarettes, but quite lower levels of the other harmful components than combustible cigarettes. 3) The average NFDPM releases of 11 iQOS samples were 1.3 and 9.8 mg under ISO and HCl regimes respectively, which suggested that NFDPM release from the product was significantly influenced by the puffing regimes. The average NFDPM releases of 3 glo samples were 2.9 and 7.0 mg under ISO and HCl regimes respectively, which had a similar NFDPM release pattern to combustible cigarettes under the two puffing regimes.