Laser-induced breakdown spectroscopy (LIBS) is a material composition detection technology that has emerged in recent years with the development of laser technology and spectral detection technology. This technology has many advantages such as fast, non-destructive, simple operation, and no sample pretreatment , but the traditional LIBS has the shortcomings of weak spectral intensity and low SNR, which directly affects the accuracy of quantitative analysis.To enhance the laser-induced breakdown spectrum intensity and improve the SNR, some different cavities were designed (height of 1 mm, diameters of 2, 3, 4 , 5, 6 mm; Diameter of 5 mm, heights of 1, 2, 3, 4, 5, 6 mm), the Au-NPs (Au nanoparticles) (diameter of 10, 20, 30 nm) was combined with the cavity to confine the plasma spectrum of the sample. Experiments show that the optimal cavity diameter is 5 mm and the height is 4 mm, the optimal Au-NPs size is 20 nm. Compared with the traditional LIBS, under the optimal cavity, Au-NPs and the combined action of the optimal cavity with Au-NPs, the enhancement factors are 20.6, 7.3, and 31.3, respectively. The cavity can increase the plasma electron temperature and Au-NPs have almost no effect on the electron temperature. Both the Au-NPs and cavity can improve the SNR. Under the combined action of the optimal cavity and the optical Au-NPs, the SNR is the highest.