Abstract: An attenuated vaccine strain of Duck Paramyxovirus(DPMVa) was selected and obtained by passage serial within SPF chicken embryo fibroblast(CEF), and some biological property of it were detemined. The DPMVa was non-pathogenic to Muscovy ducks without maternal antibody; and was non-viulence through five serial passages in one-day-old Muscovy ducks; TCID50 to CEF stable between 10-6.0~10-6.5·(0.1 mL)-1. The protection rate of the attenuated strain was above 90% when challenged with a virulent strain of DPMV 7 days after vaccination. The results indicated that attenuated vaccine strain had excellent safety, effective immunogenicity and genetic stability, which could be used as a vaccine against DPMV.