Chicken anemia virus (CAV) encodes a small protein, VP3. A fusion gene construct which can express the fusion protein of enhanced green fluorescence protein (EGFP) and VP3 in eukaryotic cells, was transfected into five cell lines, human hepatoma cell strain Smmu7721, HepG2, rat hepatoma cell strain HTC, human embryo kidney cell stain 293 and mouse fibroblast cell stainΨ2.The green fluoresence was observed within the nuclei of the strains. While the control plasmid, which can express only enhanced green fluorescence protein in eukaryotic cells, was transfected into these cell strains，the green fluorescence was observed around the whole cytosol. This means that VP3 has the function of nuclear localization in these cell strains. After the analysis of the amino acid sequence of VP3, a domain of the amino acid sequence of the protein that has the character of nuclear localization sequences (NLS) was found. Deletion of this domain from VP3 led to the deprivation of nuclear location in human hepatoma cell strain Smmu7721. This domain was subcloned and fused to EGFP. The fusion gene construct was transfected to human hepatoma cell strains. The green fluorescence could be seen again to locate mainly in the nuclei. Deletion of the basic amino acids region near the C end of VP3 also led to the deprivation of nuclear location. The prediction of the secondary structure of VP3 shows that the basic amino acid region near the C end can form a β-sheet. This means that the basic amino acids region near the C end is very important for VP3 nuclear localization. The domain maybe the NLS of VP3. After a vector that could only express VP3 was transfected into Smmu7721 and stained the cells with propidium iodide (PI), the primary evidence of VP3 inducing apoptosis was obtained.