Abstract: Based on the FSAM model(Schmid,1994), footprint and source area functions were calculated according to the continuous flux measurement with the open path eddy covariance system from Jan 1,2003 to Dec 31,2003. The spatial representative of flux measurement of the mixed forest of Broad-leaved and Korean pine in Changbai Mountain was explained. The results showed that:① under unstable stratification, source areas were smaller than those under stable conditions, and source areas in the dormant season are larger than those in the growing season at the same level;② in the prevailing wind direction 200°-290°, the upwind range of source areas was in the magnitude of 0 600 m and vertical upwind range was -300-300 m at a 0.8 level under unstable stratification in the growing season. Under the stable stratification, they were 0-1500 m and -1 000-1 000 m. In the dormant season, the range was larger. In the other wind directions, the ranges were similar than those of the growing season in the prevailing wind direction under the same atmospheric conditions; ③ in 2003, 76% of the flux information came from the relatively homogenous mixed Broad-leaved and Korean pine forests from northwest to southwest, and the source areas of the maximum footprint were located in the range of 100-400 m southwest. There was little information from the town northeast. Only about 3% information came from other surfaces apart from 0.5 km east.