Laser-induced breakdown spectroscopy can be used to detect the effective content of heavy metal ions in soil. The basic principle of emission spectrum from excited plasma is summarized. And the experiment apparatus are designed. A semiconductor solid state laser is used as an excitation light source and a spectrometer is used as a receiver. The spectrum lines of metal ions in selected soil are obtained. Compared with spectrum line graphs of standard metal ions, the content of heavy metal ions in soil is obtained. Whether the soil is polluted or not is determined. The experiments prove that the method is feasible to be used in soil detection.