A laser-induced breakdown spectroscopy system integrated with a micro-imager is developed. The energy stability of laser and background noise level of spectrometer are analyzed with the descriptive statistical method. The stability features of laser-induced breakdown spectroscopy signals in gas and solid samples are emphatically analyzed and compared. The results show that the laser-induced breakdown spectroscopy signals of air have the characteristics of random fluctuation and normal distribution. The laser-induced breakdown spectroscopy signals of aluminum alloy have the characteristics of position sensitivity and non-random fluctuation. Compared with that of the air sample, the instability of laser-induced breakdown spectroscopy signal of the aluminum alloy sample is mainly due to the change of the light-matter interaction region. The stability can be effectively improved by multi-pulse averaging for the laser-induced breakdown spectroscopy signals with normal distribution characteristics.