Abstract: 【OBJECTIVE】To study the genetic variation of field virulent CSFV. 【METHOD】 The special primers were designed and synthesized according to the full E2 sequence of CSFV Shimen strain published in GenBank. The E2 gene of field virulent strain that was collected from Henan province was amplified by RT-PCR and cloned into pGEM-T vector. The nucleotide sequence was determined by sequencing and the amino acid sequence was deduced. 【RESULTS】The result showed that the full fragment of E2 gene was cloned. Compared with the corresponding region of HLCV, C, Shimen, Alfort and Brescia strain of CSFV, the nucleotide sequence homology was 99.0%, 96.5%, 93.5%, 94.4% and 89.9% respectively. And the amino acid homology was 97.8%, 94.0%, 92.6%, 92.0% and 91.0%, 87.0% respectively. The further study of the field strain was done by the phylogenetic tree. The filed sequenced strain has closer relation with HLCV strain compared with the Shimen, Alfort and Brescia strain. 【CONCLUSION】The result showed the isolated CSFV strain has high homology with the vaccine strain, suggesting that little mutation was occurred in the strain we cloned, and the current CSFV vaccine could provide whole protection for this virulent area in some extent.