To improve the quality of laser-induced breakdown spectroscopy, nanosecond pulse laser generated by Nd∶YAG laser was used to excite soil sample. The intensity and signal-to-background ratio of Al Ⅰ 394.401 nm, Ba Ⅰ 455.403 nm, Fe Ⅰ 430.791 nm and Ti Ⅰ 498.173 nm were observed using a grating spectrometer and a photoelectric detection system. The effects of laser shot frequency（5, 10 and 15 Hz）on the radiation characteristics of laser-induced plasma was studied. The experimental results show that as compared with the laser shot frequency of 5 Hz, the spectral line intensity of Al, Ba, Fe and Ti increased by about 50.94%, 112.7%, 107.46%, and 99.38% at 15 Hz respectively under the same laser energy, while the spectral signal-to-background ratio increased byabout 15.16%, 24.08%, 40.26% and 72.06% respectively. The effects mechanism of the laser shot frequency on radiation characteristics of plasma is explained by measuring plasma parameters.