Abstract: The identification and Growth Characteristics of the pathogen of Valencia orange green spot were studied. The results showed that Valencia orange green spot was a new disease caused by Apatococcus lobatus of Chlorophyta. Apatococcus lobatus could acclimate to a large range of temperature shift. The temperature range for the pathogen growth was 5~30℃ with the optimum of 15~25℃. Apatococcus lobatus also has a wide range of light intensity adaptability. Under illumination of 500lx to 4000lx it could grow, optimal range of light intensity was 1000lx~3000lx. Apatococcus lobatus could grow in the condition of pH 4~10, optimal range of pH was 5~9. Field observation of the disease development was carried out. The results indicated that the disease development had close correlation with RH. The disease occurred seriously when RH was not lower than 80%.