The invention discloses an infrared multi-constituent monitoring method and a monitoring system for monitoring emission flux of gas in pollution sources, which is characterized in that the monitoring system comprises a movable platform which is provided with a solar tracker, an infrared spectrometer, a computer and a GPS localizer; The monitoring method comprises the following steps: taking the sun as a light source, which penetrates the polluted gas and is absorbed selectively by the gas molecule; guilding the sunlight into the infrared spectrometer by the solar tracker and measuring the solar spectrum; analyzing and calculating the column concentration of the pollutant molecule by a software; moving the movable platform and measuring the column concentrates of different positions; measuring the distances of different points by the GPS localizer; furthermore, and obtaining the emission flux of the pollution gas in the whole measurement area by the calculation of the software by combining the wind speed information of all measuring points,. In the invention, the emission flux of the gas in the pollution source can be monitored quickly and exactly, the whole set of system is simple for operation, the cost is relatively cheap, the monitoring process is completely controlled automatically by the software, with convenient use.