The atmosphere itself can not only emit hydrodynamic waves and electromagnetic waves of various frequencies, but also produce classical physical or quantum physical effects such as refraction, scattering, absorption and dispersion when these waves propagate in the atmosphere. Due to these influences, when the atmospheric state of atmospheric components such as concentration, temperature, air pressure, airflow, fog and precipitation changes, the physical characteristics of wave signals such as frequency spectrum, phase, amplitude and polarization will change in a variety of specific ways, thus storing rich atmospheric information and transmitting it to distant places. This kind of wave is called atmospheric signal. It is the basic task of atmospheric remote sensing research to develop experimental equipment that can transmit, receive, analyze and display various physical characteristics of atmospheric signals and establish the theory and method of extracting atmospheric information from the physical characteristics of atmospheric signals, that is, inversion theory. Therefore, a series of new technological achievements, such as infrared, microwave, laser, acoustics and electronic computer, must be applied to reveal the physical mechanism and laws of the formation and propagation of atmospheric signals in the atmosphere, distinguish the characteristics of atmospheric signals under different atmospheric conditions, and establish an atmospheric remote sensing equation describing the quantitative relationship between the physical characteristics of atmospheric signals and the concentration of atmospheric components, the state of motion and the spatial distribution of meteorological elements. These theories involve not only physical problems such as mechanics and electromagnetism, but also atmospheric dynamics, atmospheric turbulence, atmospheric optics, atmospheric radiation, cloud and precipitation physics, atmospheric electricity and other atmospheric physical problems.