In order to explore the cause of the difference in the pathogenicity of the different strains of porcine parvovirus (PPV), the amino acid site differences of the non-structural protein NS1 of PPV NADL-2 and Kresse strains were compared by using bioinformatics online softwares,and a series of online softwares were used to compare the differences of physicochemical property,hydrophobicity/hydrophilicity and signal peptide between them,and then analyze their domain,secondary structure and tertiary structure.The result showed that there were significant differences in amino acids at 621—636 sites between the two strains.The hydrophobicity of Kresse strain was weak,and in the secondary structure it contained more curly structures. Through the comparison of the tertiary structures combining the above results,it was inferred that the difference in pathogenicity between the two strains was due to the different domains of unknown functions at 621—636 sites.