The work aims to investigate the effect of hot water treatment on green mold control of harvested lemon fruits and the inhibition mechanism of Penicillium digitatum (P. digitatum) in vitro in view of the green mold of harvested lemon. With Citrus limon (L.) Burm as the experimental material, the effect of hot water treatment at different temperatures and time on the control of lemon fruits' green mold was studied, and the effect of hot water treatment on the viability and pathogenicity of P. digitatum in vitro was explored. The pathogen was isolated from the lemon fruit with typical symptoms of green mold and identified as P. digitatum. The suitable hot water treatment conditions at 53 ℃ for 3 minutes could effectively control the green mold of harvested lemon compared with the control group, the disease incidence and lesion diameter of lemon fruits were respectively reduced by 93% and 97% after 5 d storage. In vitro, the growth of P. digitatum could be significantly inhibited by hot water treatment, its cell membrane permeability could be changed, and the inoculated disease incidence of P. digitatum treated by hot water was remarkably reduced (P<0.05). In this experiment, the hot water treatment conditions at 53 ℃ for 3 min can significantly control green mold of lemon fruits caused by P. digitatum and decrease the viability and pathogenicity of P. digitatum in vitro.