Abstract: To keep track of the pathogenicity and genomic features of avian paramyxovirus type 1 prevailing in ducks, virulence to different animals and genome sequences of two isolates as well as its genetic diversity and evolution were determined. Phylogenetic analysis showed that M4 shared a high identity with vaccine strain Ulster and belonged to genotype I, while PX2/03 isolate clustered with those virulent waterfowl isolates, such as FP1/02, which were belong to genotype VIII. Genome sequencing results showed that the genome size of M4 is 15186 bp, which is six bp shorter than that of PX2/03, and despite the fact that the two isolates shared a high identity of 92.3% with each other, they distinct significantly in pathogenicity. M4 strain was almost nonpathogenic while PX2/03 was highly pathogenic to chicken and different species of ducks. Additional, animal experiment results indicated that Muscovy duck was more susceptible to PX2/03 isolate than Mule duck or cherry valley duck does despite the similar fatality of these animals after infected with strain PX2/03.