The internal waves are a type of sub-mesoscale wave motions occurring in the interior of stratified ocean, which is an indispensable component for physical oceanographic research, particularly for ocean mixing and energy cascade studies. The huge shock momentum suddenly generated by internal solitary waves may lead to catastrophic threats to underwater navigations and ocean engineering facilities. Thus, implement of real time monitoring and forecast for ocean internal waves is of great significance for operational applications. The South China Sea is one of ocean areas in the global ocean, which are characterized by frequent occurrence of super intensive internal waves. Long-term mooring observations show that the internal solitary wave amplitudes reach as high as 150–200 m in west of the Luzon Strait, occurring all year round. Therefore, the South China Sea is a hotspot ocean area for observation and research of ocean internal solitary waves. Based on the literature published from 2015 to 2021, this overview paper aims to review recent advances in the research of internal waves in the South China Sea. It is recognized that the research results have gained a qualitative rise during the 7 years. First, it is implemented that major observation technologies have been raised from 2D satellite observation to 3D simultaneously combined observation of satellite and mooring technologies. This technologic advance has promoted a series of innovative results, such as super intensive internal solitary wave with the amplitude as high as 240 m, mesoscale eddy modulation to the internal waves, the internal solitary waves with the re-appearance period of 23 h, fission phenomenon of internal solitary waves in the shallow waters, internal waves in the deep basin and their energy cascade. Second, the study areas have appeared an expanding trend to the central deep basin. Up to now, the study areas of observation and research of internal waves in the South China Sea have been concentrated in west of the Luzon Strait and on the northern continental shelf. Fortunately, there is a trend to expand the study areas to the central deep basin. Third, applications of cutting-edge technologies for ocean detection to the observation and research of internal waves in the South China Sea have promoted innovative results. The M₂ internal tide radiation beam images derived from satellite altimeter along track sea level fields by 2D plane wave decomposition techniques solved the issues on generation mechanisms and source regions of internal waves in the northern South China Sea, which have been debated for many years. AI technology has been successfully applied to develop forecast models for internal wave propagation in the adjacent marginal seas of the South China Sea. The average root–mean-square difference between the model-forecasted and satellite-observed internal wave leading crest lines after one tidal cycle was 3.21 km. The corresponding averaged correlation coefficient was 0.95. Rapid-sampling deep profiling float technology has been tested in the northern deep basin of the South China Sea. The test obtained vertical distribution of water temperature fluctuation amplitude induced by 0.1–1.8 d band wave motions of full depth from 0 to 3500 m. High-resolution underwater imaging technologies, including marine multichannel seismic imaging technique and acoustic backscattering technologies, have been successfully applied to the observation and research of internal waves on the northern continental shelf of the South China Sea. The spatial resolution of acoustic backscattering images reaches 10 cm. The images clearly show fine structures inside the internal solitary wave packet, including the characteristic half width with a horizontal scale of 2 m only. It is expectable that abundant accumulation of research results, particularly successful application cases of AI technology to set up forecast models for internal wave propagation, would certainly establish a solid base for development of accurate forecast models for internal waves in the South China Sea.