According to the need of heavy metal pollution detection in waste water. Pure graphite flake is selected as matrix material, the LIBS method of multiple enrichment of samples combined with spatial confinement is adopted to detect the heavy metals contained in the waste water, and spectral stability and limit of detection of Pb, Cu, Cd and Ni are also analyzed. The experiments uses a wavelength of 1 064 nm Nd∶YAG Laser, and a optical spectrometer, which the resolution is less than 0.1 nm to detect the characteristic spectrum of heavy metal elements content in water. The result shows that this method serves to improve sensitivity and spectral stability of heavy metal in waste water while reducing the limit of detection of heavy metals. The intensity of characteristic spectrum are about 2.5 times better than it under the condition of non-confinement, the spectral stability has also been improved, RSD is reduced from 11.34% to 8.77% compared with non-confinement condition. The calibration curves of four heavy metal elements have been established, the limits of detection of Pb, Cu, Cd and Ni are lower than 1/6 of discharge standard of national industrial waste water, meeting the demand of heavy metal in industrial waste water online monitoring. This method provides a convincing support for discharge control and online monitoring of warning excessive discharge of heavy metal elements in industrial waste water.