As one of the core devices in optical systems for interconnect, communication, and sensing, electro-optical modulators are in charge of the critical functionality of electric-optical signal conversion. Silicon electro-optical modulators based on silicon on insulator (SOI) exhibit various advantages such as compact size, high modulation efficiency, and CMOS fabrication compatibility. Therefore, they have been a hot topic for years and are being commercially deployed on a large scale. Furthermore, the popularization of artificial intelligence and rise of hyper data centers continuously drive the development and innovation of electro-optical modulators. This review first introduces the two principles of silicon electro-optical modulation—free carrier plasma dispersion effect and DC Kerr effect—followed by the common modulation mechanisms and classical forms of devices. Subsequently, we present recent typical innovative advances in high-speed optical interconnects, microwave photonics, and optical sensing. Finally, we summarize the development status and opportunities of silicon electro-optical modulators and discuss the existing challenges, emphasizing the importance of the original innovations of the modulation principle.