Abstract: Effect of nitric oxide(NO) donor sodium nitroprusside(SNP) on the growth,colonial morphology and microstructure of Alternaria alternata were studied in vitro,and its curative and preventative effect for apple black spot control were also evaluated. The results showed that SNP could significantly inhibit spore germination and mycelia growth of A. alternata and the effect was in dose dependent manner. The inhibitory ratios of spore germination and mycelia growth reached to 70%,and 75.9% respectively when treated with 1 g/100 m L SNP.Rough surfaces,uniform thickness,distorted cell and ruptured cell membrane were observed after treatment with SNP by scanning electron microscopy(SEM) and transmission electron microscopy(TEM). Meanwhile,SNP treatment not only could cure the black rot on inoculated apple,but also induce the increase of fruit resistance to prevent disease developmemt,the optimum inhibitory concentration was 0.5 g/100 m L SNP. Results suggested that NO,as a safe preservative alternative to synthesis fungicide,might have potential application for postharvest disease control.