In this research use Penicilium italicum which causes the major loss of citrus fruits during storage and distribution as the research object,and in vitro and in vivo evaluation to determine the antibacterial activity of ammonium carbonate and ammonium bicarbonate. The effect of ammonium carbonate and bicarbonate on conidial germination and mycelium growth of P.italicum was evaluated. Inhibition of both compounds on disease incidence of citrus fruits either naturally or inoculated with the pathogen was also investigated. The results demonstrated that ammonium carbonate and bicarbonate demonstrated powerful inhibitory effect on spore germination and mycelium growth of the pathogen with the minimum inhibition mass fraction for spore germinations of 0.32% and 0.36% respectively. The inhibitory effect of both compounds on the pathogen was quite stable after the solutions were treated under different temperatures (4-100℃) for 30 minutes.Both compounds demonstrated strong inhibition with the media at neutral and alkaline pH. Both compounds at the mass fraction of 0.80% could significantly reduce the decay rates of citrus fruits either naturally or inoculated with the pathogen. 