Natamycin (also known as pimaricin) has been widely used as an antimycotic agent in food industry. In this study, we showed that natamycin application had a high inhibitory effect on the vegetative growth of two important postharvest pathogenic fungi, Botrytis cinerea and Penicillium expansum. Application of 100 mg L^-1 of natamycin could completely inhibit the occurrence of grey mould disease in grape fruit and 200 mg L^-1 of natamycin was required for controlling blue mould disease in jujube fruit. The inhibitory effect of natamycin on the infection process was mainly due to its direct inhibition on spore germination. To further investigate the mechanisms by which natamycin inhibited fungal growth, we inspected the integrity of plasma membrane of B. cinerea and P. expansum. The results indicated that natamycin can damage the plasma membrane of pathogenic fungi, leading to the release of intracellular contents and eventual cell death. Taken together, our data suggest that natamycin had a high efficiency on controlling postharvest diseases. The low toxicity to mammal and broad antimicrobial spectrum of natamycin make it a promising alternative of chemical fungicide to control postharvest diseases.