The release of CO during the cigarette smoldering and puffing periods was firstly studied by combining a dedicated modern experimental approach for quantifying gas-phase temperature with the tobacco pyrolysis and combustion reactions system, which guarantees more accurate reaction conditions were used to mimic the thermal environment inside a burning cigarette. Basing on the two cigarette paper burn lines (PBL) at smoldering and puffing, the cigarette burning zone were divided into three regions. The first region was in front of the PBL at 0 s (R1), the second region was between the two PBL (R2) and the third region was behind of the PBL at 2 s (R3). The experimental results show that: ① R1 and R2 exposed to high temperatures at smoldering and produced much CO for side stream smoke, therefore less CO was generated for mainstream smoke in R1 and R2; ② during the puffing period, R3 had the lowest temperature distribution, but contributed most to the release of CO in mainstream smoke; ③ because of the influence of the heat conduction, the temperature of R3 would rise at puffing with the increment of the temperatures inside the cigarette at smoldering, resulting to the increase of CO in mainstream smoke.