In order to improve detection sensitivity and reproducibility of metal element analysis in aqueous solutions using laser induced breakdown spectroscopy (LIBS), a paper slice has been used as a liquid absorber to transform liquid sample analysis to solid sample analysis. Calibration curves for metal element Pb under different concentrations have been obtained. The results demonstrate that the analysis accuracy and error of detection limit produced by the internal standard method are more precise than those in absence of internal standard. Mn is chosen as the reference element. With optimized experimental parameters, such as the delay time for LIBS signal detection, gate width and pulse energy, the detection limit of Pb is determined to be 3.87 mg/L, which is lower than those obtained by similar detected methods. The detection sensitivity is about ten times higher than that in our previous experiments, in which the laser pulse is focused on the surface of the liquid jet. The paper sample is very easy to handle so that the detected time can be greatly shortened. As the lower pulse energy is needed, this approach provides a more practical approach for metal element analysis in aqueous solutions by using LIBS.