There is an urgent need to develop a rapid on-site green detection technology for the growing heavy metal pollution of fruit and vegetables. Laser induced breakdown spectroscopy (LIBS) is an emerging technology in detecting material composition. In order to verify the feasibility of the detection of heavy metals in leafy vegetables by LIBS this article discusses the application of LIBS to quantitativly analyze trace elements theoretically. With fresh ipomoea aquatica as the sample, the spectra with and without Pb pollution are analyzed using coaxial double pulse LIBS device. Pb 405.78 nm is selected as the spectral line of Pb, seven samples emission spectra are detected, and fitting curve is obtained, the correlation coefficient is 0.9857. Relative error of predicted concentration from calibration model is between 0.928% ~15.05% , with an average of 8.31% , and when in high pollution level it is less than 3% . The test results show that, the feasibility of LIBS detecting heavy metal elements in ipomoea aquatica is proved.