Laser-induced breakdown spectroscopy (LIBS) is a new material identification and quantitative analysis technology developed in the past twenty years, which has unique features including the simplicity of method, being rapid, simultaneous multi-element detection and being non-destructive to sample. The traditional LIBS technology has a weak emission line spectrum, resulting in poor detection accuracy. Applying cavity confinement or depositing nanoparticles on the surface of the sample can significantly enhance the intensity of plasma emission spectrum, and the accuracy of detection and quantitative analysis can be effectively improved. However, the survival time of plasma is very short, usually between 1 and 10 μs. The acquisition time delay is too short and will be collected together with the background noise, while the acquisition delay time is too long, the acquired spectral intensity may be low, so it is important to choose the appropriate acquisition delay time for obtaining spectral data. Focusing on the time evolution of LIBS under the action of cavity confinement and nanoparticles, the alloy samples were used to generate plasma, and the time-resolved spectra of plasma at the acquisition delay time from 0.5 to 5 μs were collected. Ni Ⅱ 221.65 nm and CⅠ 193.09 nm were selected as the target lines, and the changes of spectral line intensity, enhancement factor and signal-to-noise ratio (SNR) were analyzed. Experimental results showed that under the unconfinement, cavity-confinement laser-induced breakdown spectroscopy (CC-LIBS), nanoparticle-enhanced laser-induced spectroscopy (NELIBS) and the above two cases worked together, as the acquisition delay time increased, the spectral intensity decreased in turn. When the cavity confinement was applied, the intensity of spectral line became very low after the acquisition delay time was greater than 2 μs. When nanoparticles were deposited on the surface, a considerable amount of plasma could still be collected even if the acquisition delay time was greater than 3 μs. When the acquisition delay time was 1us, the enhancement factor under dual action was the highest, reaching 2.1. When cavity confinement was involved, the spectral intensity was lower than that without confinement after the acquisition delay time was greater than 3 μs. When only the nanoparticles were deposited, the SNR was optimal, reaching 9.52. Under the condition of dual constraints, the trend of SNR was basically the same as that with only cavity confinement. Nanoparticles are helpful for the detection of trace elements in samples in the whole acquisition delay time range, while cavity confinement inhibits the detection of trace elements when the acquisition delay time is large.