Continuous emission monitoring system (CEMS) is composed of four basic parts: smoke monitoring subsystem, gaseous pollutant monitoring subsystem, smoke parameter monitoring subsystem, system control and data acquisition and processing subsystem. It can monitor SO2, NOx, O2, dust, temperature, pressure, flow rate and other parameters in the gas. It can also expand the monitoring of HCl, HF, Co, CO2, humidity and other parameters for specific occasions. The measured gas passes through the sampling probe for dust removal, the heat tracing tube for sampling, and enters the high temperature gas analysis module (DOAS and TDLAS Technology) for analysis and measurement. It effectively solves the technical problems such as low measurement results caused by water precipitation and absorption of SO2 by condensation method, and has incomparable advantages especially in low concentration measurement occasions.