The invention discloses a grass carp haemorrhagic virus resisting engineered protein TAT (Trans-activating Transcriptional Activator)-VP7-TAT as well as a preparation method and application thereof. The amino acid sequence of the TAT-VP7-TAT protein is shown as SEQ ID NO:2, and a corresponding nucleotide sequence is shown as SEQ ID NO:1. By using Eschierichia coli BL21(DE3)/pET-32a-TAT-VP7-TAT to perform inducible expression for 4 to 5 hours, a TAT-VP7-TAT fusion protein can be efficiently expressed; the N end and the C end of the protein are respectively provided with protein transduction domain polypeptide TAT. The genetic engineering fusion protein provided by the invention can be used for preventing grass carp haemorrhagic virus diseases. The fusion protein has the advantages of high expression, easiness for industrial production, low cost and good safety; grass carp orally takes the fusion protein, so that better immune protection is realized.