As the Ministry of Ecology and Environment promotes ultra-low emission retrofitting in the cement industry, higher requirements are placed on flue gas treatment and online monitoring systems. This paper systematically compares the detection method standards and technical principles of SO2, NOX, and NH3 for stationary pollution sources at home and abroad, focusing on the analysis of eight analytical techniques, including differential optical absorption spectroscopy (UV-DOAS), ultraviolet fluorescence (UVF), chemiluminescence detection (CLD), and tunable diode laser absorption spectroscopy (TDLAS). Combined with sampling systems such as cold-dry extraction, hot-wet extraction, dilution extraction, and in-situ direct measurement, this paper evaluates the applicability of these techniques under complex operating conditions in cement production. The research shows that the in-situ hot-wet system based on UV-DOAS offers advantages such as fast response, high accuracy, low power consumption, and low maintenance, making it particularly suitable for SCR denitrification process control and ultra-low emission monitoring. Verified by typical application cases, the UV-DOAS combined with in-situ hot-wet extraction monitoring system demonstrates stable performance and accurate data in SCR denitrification process and kiln tail flue gas outlet monitoring, meeting national technical specification requirements. In the future, with increasing demand for ultra-low emissions and multi-component monitoring, domestically produced Fourier transform infrared (FTIR) analysis systems are expected to become a better solution.