Abstract: In this paper, studies on armandii pine (Hua shan pine) blister rust inYunnan are reported. The morphology of the rust is basically the same as Cronartium ribicola from Sichuan and North-east of China. But some significant diffrereces are observed in the super microstructures of the aeciospores and urediospores:the number of the annulate on the verrucose is 5~7, which is 4~5 in Sichuan and 7~8 in Liaoning. Artificial innoculation experiments verified that, in Yannan, the alternative host of the rust is Ribes glacial and the rust didn't infect Ribes glacial var. laciniatum (the alternative host of C. ribicola in Sichuan). According to studies on the morphology and alternative host of the parasite, it is thought that the rust of Yunnanis C. ribicola f. sp. ribicola and the varied enviroments cause the rust to differ from other five-needle blister rusts in super microstructures. The experiments of aeciospore germination showed that:(1)Aeciopores started to germinate at an optium of 20℃ and over arange of 4~36℃. (2) Aeciopres could germinate when the humidity was over 35% RH and the optium humidity was 100% RH. (3) Aeciospores germinated best under natural condition of alternative ligh and darkness. (4) About 90% aeciospores couldn't germin ate in the lab condition and the germination reached its peak in the first 24 hours.