Objective To develop an effective method for inhibiting Botrytis cinerea in tomatoes.Methods The effect of the addition amount of nanomaterial and light exposure time in chiral gold-modified TiO₂ (DAT) composite materials on the inhibition of B. cinerea in tomatoes was studied through colony diameter and antibacterial rate. The mechanism of action of DAT on B. cinerea was explored by analyzing mycelial biomass, nucleic acid and protein leakage, and fungal cell structure.Results When the chiral nano-gold addition was 80 μL, the DAT concentration was 5 mg/mL, and the natural light exposure time was 24 hours, the highest inhibition rate of DAT against B. cinerea was 53.64%. DAT nanomaterials generated free radicals under light exposure, disrupting the cell membrane, causing extensive leakage of fungal nucleic acids and proteins, and inhibiting the growth of B. cinerea mycelia. The surfaces of B. cinerea mycelia treated with DAT were rough, wrinkled, and damaged, effectively destroying the mycelial structure of B. cinerea.Conclusion DAT can effectively destroy the cell membrane and mycelial structure of B. cinerea in tomatoes, inhibiting the growth and reproduction of B. cinerea.