Cavity formation is a common phenomenon involved in solid-state analysis when repetitive laser pulses are applied to induce breakdown spectra. While previous LIBS investigations have been mostly focused on laser ablation on flat surfaces, the development of a laser-induced plasma inside cavity structures is of both fundamental and practical significance for quantitative chemical analysis using LIBS. In this paper, we attempt to answer the question, to what extent cavity formation would influence the temperature and electron density of laser-induced plasma. We found a significant effect of cavity aspect ratio on plasma characteristics, in particular, the measured high temperature and electron density of laser-induced plasma inside cavity structures.