Citrus black spot disease is one of the important diseases on citrus. In this paper, the pathogen causing the citrus black spot disease was identified on Citrus reticulate Blanco cv.Tangerina in Minhou County, Fujian Province, based on Koch′s postulates and rDNA internal transcribed spacer(ITS) sequences. The sample was collected on July 2009. The colony growing slowly from the PDA medium plate was round and protuberant. The spherical pycnidium was black and the monadic conidiophore elliptic， colourless, (7~12) μm×(5~8) μm, surrounded by a layer of translucent gelatinous coat. The ITS sequence analysis proved that the pathogen was Guignardia citricarpa Kiely. This is the fourth confirmed record of this pathogen from China. This research laid a foundation for early diagnosis and treatment of citrus black spot disease.