To study the effects of low temperature treatment of cut filler on the contents of moisture and CO in mainstream cigarette smoke, the cut filler leaving the flavoring cylinder was directly kept under low temperature of -5, -10, -15 and -20 °C for 10, 20 and 30 minutes, respectively. The contents of moisture and CO in mainstream smoke of the cigarettes made of the cut filler were determined. The results showed that: 1) The moisture content in cigarette smoke increased, while CO content decreased comparing with the control. 2) For the same treatment duration, moisture content in cigarette smoke increased first and then decreased as the fall of temperature, the greatest increase rate was 7.66%; while CO content decreased first and then increased, whose greatest decrease rate was 7.58%. 3) For the same treating temperature, the moisture content in cigarette smoke increased first and then decreased with the prolongation of treatment duration, while CO content decreased gradually. It was concluded that proper low temperature treatment of cut filler is beneficial to the increase of moisture content and the decrease of CO content in cigarette smoke