In this research, the introduction of chirality into carbon quantum dots (CQDs) successfully facilitated the formation of chiral carbon quantum dots (CCQDs). These CCQDs manifested excellent photophysical properties. Moreover, chirality was exploited as a key factor to modulate the optical power limiting (OPL) properties of the CQDs. Chiral activities of precursors l/d-threonine (Thr) and l/d-cysteine (Cys) were used to prepare l/d-ThrCQD and l/d-CysCQD, respectively. The OPL performance of l/d-CysCQD was better than that of l/d-ThrCQD, because the band gap of l/d-CysCQD, containing N and S elements, was smaller than that of l/d-ThrCQD doped with N atoms. The carbon core formed by combining N and S atoms with sp