The CO2 concentration in broad-leaved Korean pine forest of Changbai Mountains was measured continuously with a CO2 infra-red analyzer in 2003. The results showed that the CO2 concentration in the forest had striking characteristics of temporal-spatial variations, which were mainly influenced by the physiological processes of plants, soil respiration, and intensity of turbulence exchange. In growing season, the daily maximum and minimum CO2 concentration appeared mostly on the surface floor at about 5:00 in the early morning and at canopy location at about 15:00 in the afternoon, respectively. There was an obviously process of forest CO2 emission when the inversion broke at dawn. The average CO2 concentration in forest was 377 micromol x mol(-1) in 2003, the maximum of monthly average appeared in January as 388 micromol x mol(-1), and the minimum of monthly average appeared in August as 352 micromol x mol(-1). The forest acted as CO2 source in night time and turned to sink in daytime, during growing season. In non-growing season, the forest acted as CO2 source in both daytime and night time, but still had a clear evidence of CO2 assimilation at noon, with canopy location during non-growing season.