A method for quantitatively detecting infectious hypodermal and haematopoietic necrosis virus (IHHNV) in a biological sample, comprising the steps of obtaining a primer pair having nucleotide sequences set forth in SEQ ID NO: 1 and SEQ ID NO: 2, and a fluorescent probe having a nucleotide sequence set forth in SEQ ID NO: 3; amplifying a non-structural protein coding region of the virus in the biological sample by a real-time polymerase chain reaction (PCR) using the primer pair and the fluorescent probe; and determining the presence and quantity of the virus in the biological sample with reference to a positive control plasmid.