<p><i>L</i>-cysteine-activated copper nanoparticles and <i>D</i>-cysteine-activated copper nanoparticles were synthesized using sodium dodecyl sulfate as a stabilizer and dispersant, and cysteine as a chiral ligand. These copper nanoparticles exhibit significant enhanced circular dichroism (CD) signal due to their plasmon resonance amplification. By leveraging intermolecular interactions between the amino acids on the surface of copper nanoparticles and chiral amino acids in the sample solution, a quantitative CD optical sensing method for the enantiomeric analysis of amino acids was developed. Within the concentration range of 1.2–3.2 mmol/L, the optical activity intensity of the active nanoparitcles exhibited a good linear relationship with the concentration of enantiomeric amino acid. The detection limits (3σ) were 0.71 mM for <i>D</i>-cysteine using <i>L</i>-type active nanoparticles, and 0.63 mM for <i>L</i>-cysteine amino acids using <i>D</i>-type active nanoparticles. This method achieved quantitative CD optical sensing for the analysis of enantiomeric amino acids. The approach is rapid, convenient, and highly sensitive, demonstrating potential application for the detection of bioactive substances such as amino acids.</p> Graphical abstract <p>A novel CD sensing method for detecting chiral amino acids using <i>L</i>-cysteine active copper nanoparticles (CuNPs@Lcys) and <i>D</i>-cysteine active copper nanoparticles (CuNPs@Dcys) was developed.</p>