Ammonia (NH₃) is an important alkaline gas in the atmosphere, which can react with acid gas in the air leading to the formation of haze through dry and wet deposition. Therefore, the content of NH₃ in the air is one of the important criteria for measuring the quality of air. The anthropogenic emission sources of NH₃ are mainly divided into agricultural and non-agricultural sources, with agricultural sources accounting for 80% of the total NH₃ emission, and the main agricultural sources include livestock and poultry breeding, animal husbandry excreta and nitrogen fertilizer application in cropland. Given the significant environmental effects of NH₃, accurate measurement of NH₃ emission flux from agriculture has become an important research field for establishing NH₃ emission inventory and controlling NH₃ emission. In this paper the basic principle of measuring ammonia by three infrared spectroscopy measurement techniques, namely Fourier transform spectrum, photoacoustic spectrum and tunable absorption spectrum, and the development status and applicable scenarios of the corresponding measurement techniques at home and abroad are summarized. The principle and application of eddy covariance method (EC) and backward Lagrange method (bLS), which are widely used in the estimation of ammonia emission flux from animal husbandry and cropland, and several mature NH₃ flux calculation software based on EC or BLS algorithm are also introduced. Finally, the future development direction of NH₃ measurement technology and ammonia flux emission estimation is prospected.