Volatile organic compounds (VOCs) pollution prevention is an urgent demand for national environmental protection and public health. Adsorption is one of the most effective methods to control VOC pollution. Current understanding of the adsorption mechanism is limited, which hinders its industrial application. Identifying the microscopic adsorption mechanism is a key issue that needs to be urgently addressed for the efficient treatment of VOCs. Existing conventional methods to characterize microscopic adsorption cannot directly monitor ultrafast adsorption in real-time. New theories and techniques need to be constantly developed. In recent years, terahertz waves have shown great potential in characterizing adsorption processes. Weak interactions in the adsorption process include van der Waals forces and hydrogen bonds, whose vibrational modes are in the THz band. The surface interface mobility carrier changes due to bond breaking and formation have different THz response characteristics for different concentrations. Optical parameters of THz spectra, such as absorption peaks, amplitudes, and waveforms, have been used to characterize adsorption properties. The breaking and formation of chemical bonds in the adsorption process is on the order of picoseconds. Effective information on the femtosecond timescale is not directly available due to the limitation of the THz time resolution. Continued breakthroughs in terahertz time-resolved spectroscopy in ultrafast process monitoring satisfy the need to explore ultrafast adsorption processes on time scales and lay the foundation for uncovering microscopic adsorption mechanisms. This paper reviewed adsorption law studied by terahertz waves, and ultrafast processes were researched using terahertz time-resolved spectroscopy in recent years. Finally, the development directions and major challenges of terahertz time-resolved spectroscopy in ultrafast adsorption are proposed.