This study investigates the effect of surface passivation of chalcogenide solar cells by introducing Fmoc-Gly-OH amino acids. The results show that the moderate amount of Fmoc-Gly-OH modification can significantly improve the photovoltaic performance and stability of chalcogenide solar cells. With the increase of Fmoc-Gly-OH concentration, the photovoltaic conversion efficiency firstly increases and then decreases, and the best effect is reached when the concentration is 1.0 mg/ml.XRD and SEM analyses show that the crystal structure of the Fmoc-Gly-OH modified chalcocite thin films is more regular, and the defect density is obviously reduced.XPS analysis shows that the Fmoc-Gly-OH modification is able to reduce the defect state density of the chalcogenide layer. The reduction of defects was further verified by steady-state fluorescence spectroscopy analysis. In addition, the electrochemical impedance spectra and dark-state I-V curve results of the devices showed that the Fmoc-Gly-OH modification was able to reduce the non-radiative complexation and charge transport resistance, and increase the fill factor and open-circuit voltage. Finally, the effectiveness of Fmoc-Gly-OH surface passivation in enhancing the performance of chalcogenide solar cells was confirmed by the analysis of J-V curves and box plots. This study provides new ideas and methods for surface engineering of chalcogenide solar cells, which has some practical application prospects.