The installation and operation of continuous emission monitoring system(CEMS) for flue gas provide effective means for understanding concentration and amount of pollutant discharged, and are good for safety operation and management in thermal power plant. According to the calibration of 107 sets of CEMS for flue gas in thermal power plants of Henan Province, the qualified rate of accuracy for each calibration project and common problems existed in the operation of CEMS are analyzed and summarized, and the corresponding suggestions are proposed.