Abstract: The occurance of Melampsora rust on poplars in Shanghai was studied. The sprouting and infestation of uredinia and telia of the pathogen were tested. The alternate host of the disease has not been found, and the role of telia in disease cycle was dubious. The uredinia could sprout after over-winter. The poplars inoculated by overwinter urediniospores could result in diseases. It was not found that MelamDsora rust on poplars had an alternate host in Shanghai. The overwinter uredinia may be one of the preliminary infection sources.