In order to improve the quality of laserinduced breakdown spectroscopy and derive the optimal experiment condition, the change of the radiation intensity of laserinduced stainless steel plasma with and without a small carbon chamber is analyzed, which is excited by a high energy rubidium glass pulsed laser. The mechanism of the laser induced plasma radiation intensity is discussed by measuring the electron temperature and electron density. The results show that when laser plasma is confined by a small carbon chamber with the height 9.0 mm and the internal diameter 4.0 mm, the spectral line intensities and signaltonoise ratio of the sample elements increase substantially. So the spectral quality can improve effectively by using the method of spatial confinement.