Abstract: Phyllosticta citriasiana is a new pathogen of Citrus grandis which causes black spot on the fruits, while Phyllosticta capitalensis is another fungus which is saprophytic and seprated from Citrus grandis. For distinguishing from each other, a rapid identification method named ITS-RFLP was established in this research. First of all, the target pathogens were seperated from the desease samples which were collected from the Citrus grandis Osbeck orchard at Pinghe city in Fujian. Then the mycelium total DNA were extracted for amplifying the rDNA-ITS gene fragments by using ITS1 and ITS4 primers. And then the amplification products were digested by the restriction enzyme of Acc Ⅰ. The results showed that the rDNA-ITS of P. citriasiana was digested into two fragments, and that of P. capitalensis into three fragments. Thus, the two kinds of fungi can be distinguished from each other by the fragment number and size. This technology is quite rapid and simple.