Abstract: Necrotic spot pathogen on needle of Cedrus deodara was identified as Cladosporium tenuissinum. It was a new pathogen on C. deodara. The optimum carbon source of the pathogen growth was glucose. The mycelium growth of the pathogen was obviously inhibited by nitrogen sources and vitamin. In PDA substrate, the preference temperature for mycelium growth was 15～25 ℃, and the optimum temperature 25 ℃ and pH 4. Conidia could only germinate at the relative humidity of 100%.