Abstract: The aim of this experiment was to study the genetic variability of the three different generations of porcine reproductive and respiratory syndrome virus (PRRSV) TP strain, P4, P60, P90. RT-PCR, 5′ RACE and 3′ RACE were employed to amplify the virus genome of the three generations of PRRSV TP strain, and the genomic analyses were conducted using some bioinformatics software including the clustalx and DNAStar, and the animal pathogenicity test. The sequences of the TP strain P4, P60, P90 were 15 346, 15 394 and 15 393 bp, respectively. The variations of the ORF1a gene and 3′UTR were obvious in these three generations genome sequences, especially the poly(A) tails in the 3′UTR region，they were 26, 74 and 73 bp, respectively. Comparing the genome sequences of TP P90 strain with TP P4 strain, there found 58 nucleotide mutations that resulted in 27 amino acid changes. The antigenic index and surface probability of GP5 protein of TP P90 strain were increasing than P4 and P60. Moreover, the virulence test indicated that the pathogenicity of TP P4 is stronger than the TP P60, P90 strain. The results showed that the genome sequences of the three different generations has some variations, especially between passage 4 and 60. The PRRSV TP P4, P60, P90 all belong to the PRRSV America strain branch, and display the highest nucleotide identity to the high pathogenic PRRSV JXA1 strain, 99.5%, 99.2% and 99.3%, respectively.