Laser-induced breakdown spectroscopy (LIBS) is a rapidly evolving in-situ multi-element analysis technique that has significantly advanced the field of liquid analysis. This study employs a femtosecond laser for quantitative analysis of heavy metals in flowing liquids, exploring its detection sensitivity and accuracy. Femtosecond pulsed laser excitation of water in a dynamic environment generates plasma while effectively preventing liquid splashing. The flowing water column maintains a stable liquid surface, avoiding irregular laser focusing caused by surface fluctuations. Calibration curves for chromium (Cr), lead (Pb), and copper (Cu) were established under optimized conditions at different numbers of spectral accumulations (NSAs). The limit of detection for Cr, Pb, and Cu were determined to be 0.061, 0.045, and 0.023; 0.475, 0.341, and 0.221; and 0.040, 0.027, and 0.019 μg/mL, respectively, for NSAs of 10, 20, and 50. Additionally, the R values of the polynomial fits exceeded 0.99, underscoring the reliability of the experimental approach. This study provides valuable insights into optimizing the analytical performance of LIBS for heavy metal detection in aqueous solutions, making it a powerful tool for environmental monitoring and industrial applications.