<p>The crust preserves key geological records of the Earth’s long-term tectonic evolution, hosts a variety of mineral resources, and is the source region of many natural hazards such as earthquakes and volcanic activity. Deep seismic sounding (DSS) is an important geophysical approach for investigating the structure and material composition of the crust and lithosphere. Owing to its large source energy, long observation profiles, and great investigation depth, DSS provides unique advantages and plays an irreplaceable role in probing deep Earth structures. This paper systematically reviews fundamental principles, technology, history, current status, and development trends of DSS methods. Looking forward, DSS is expected to play an increasingly important role in deep Earth exploration. Addressing key scientific questions in typical tectonic regions, as well as national strategic demands such as energy security, mineral resource supply, and environmentally sustainable development, requires further advances in related technologies. These include source technologies (e.g., air-gun sources and controlled seismic sources), observation technologies (e.g., joint acquisition of DSS and deep seismic reflection data, integrated active-passive observations based on dense short-period arrays, and distributed fiber-optic sensing techniques), and data processing and imaging methods (e.g., joint imaging of active and passive seismic data, integrated DSS and deep seismic reflection imaging, and full-waveform inversion), DSS methods will play an increasingly significant role in the field of deep structural investigation and resource exploration.</p>