Tunable Diode Laser Absorption Spectroscopy (TDLAS) provides a reliable means of on-line detection technology for sampling style escaping ammonia. Since the temperature had great effects on the 2f signal in the field environment, the results must be modified. When the temperature changed from 25 ℃ to 250 ℃, the concentrations of 100 × 10-6 NH3 were detected in the Herriott cell and the 2f signals spectrogram were obtained. The results show that the 2f signal intensity decreases and the curve smooth with the temperature rising. When the pressure changed from 20kPa to 100kPa, the results show that the 2f signal intensity decreases and the curve smooth with the pressure rising. According to the above results, the experience formula of temperature correction was raised. The formula reliability was evaluated through the correction of the 50 × 10-6 concentration NH3 in different temperatures, and the error correction was within 5.1%, which greatly improved the precision of the detection. The results show that the system is suitable for online sampling style monitoring in high temperature environment.