Laser-induced breakdown spectroscopy (LIBS) was used to analyze the P b and Cr elements in soil samples.PbI280.17nm and CrI425.43nm were used as the analysis lines,the influence of the lens to sample distance (LTSD)、delay time on the spectral signal intensity and signal-to-noise ratio SNR are optimized.Under the best experimental conditions,the spectral peak intensities and element concentrations of the two elements were analyzed,and the calibratio n curves of the spectral peak intensity and the spectral peak integral area with the corresponding element concentration were established for the external stand ard method and the internal standard method.Compared with the external standard method,the internal standard method reduces the maximum relative errors of the Pb and Cr elements from 13.56% and 12.68% to 6.7% and 5.6% by using the peak in tegral area of the spectrum to detect the heavy metals Pb and Cr in the soil;Th e fitting correlation coefficient R²of Pb and Cr element calibration curves inc reased from 0.9781and 0.9755to 0.9964an d 0.9911respectively.Experimental re sults show that the use of LIBS technology to detect Pb and Cr elements in soil is feasible,and the use of internal standard method of spectral peak integral a rea can reduce the maximum relative error and improve the measurement accuracy.