The study of cavity quantum electrodynamics based on optical microcavities and solid-state quantum systems such as quantum emitters and quantum spin systems are widely applied to modern quantum optics and quantum information science. In recent years, the study of the interaction between plasmonic nanocavity with mode volume beyond diffraction limit and high-performance two-dimensional (2D) semiconductor excitons receives extensive attention, and it is expected that such cavity-exciton system can be applied to integrated quantum optical systems. The study first introduces the weak and strong coupling between plasmonic nanocavities and 2D semiconductor excitons, and summarizes the modulation of excitonic spin-valley photonics of 2D semiconductor excitons and the coupling at the nanoscale. Then, the coupling of the nanocavity with the 2D single defective quantum emitter is introduced, demonstrating the potential application of such system in future integrated nano-optoelectronics. Finally, the challenges and opportunities for the study of plasmonic nanocavities and low-dimensional exciton systems are discussed.