For ultra-low emission flue gas monitoring, a portable high temperature flue gas analyzer based on UV differential absorption spectrum technology is developed and designed. The measurement principle, mechanical structure, optical and temperature control design of the analyzer are described in this article. The instrument is tested under different environmental conditions with different concentrations of SO2 and NOx standard gas. The test results show that the performance index of the instrument can meet the requirements of environmental protection management and environmental pollution emergency monitoring, and it has good environmental adaptability. In the future, based on the current hardware platform of the instrument, it can also be applied to the navigation monitoring in the field of atmospheric monitoring through the extended design and application development.