Laser induced breakdown spectroscopy (LIBS) has been shown to be a promising technique for element analysis with many advantages including on-line, real time, standing off and multi-element detection capability. In the present paper, the LIBS experiments for Pb in slurry samples were carried out with the motivation of developing an in-situ sensor for monitoring heavy metal. A Q-switched Nd∶YAG laser operating at 532 nm with repetition frequency of 10 Hz was utilized to generate plasma on the prepared slurry samples, which were doped with same weight manganese as reference and varied concentration of lead. The induced plasma emission was recorded by CCD. The LIBS signals at PbI 405.78 nm and MnI 403.07 nm from the slurry samples were investigated. It was found that the intensity ratio of IPb/IMn increased as a linear function of the concentration of Pb with correlation coefficient R2 of 0.994 9. The obtained results show that LIBS with conjunction of referent element could be developed as a potential technique for contamination analysis of soil slurries. The main influence factors in LIBS signal detection were also discussed.