To examine the viral growth ability in chicken embryos, a real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) method was established. According to the sequences of IBV from GenBank, primers were designed based on conservative area in the 5′-UTR. The upstream primer was 5′-CCGTTGCTTGGGCTACCTAGT-3′, and the downstream primer was 5′-CGCCTACCGCTAGATGAACC-3′. The amplification product was cloned to pMD18-T vector (Takara) as a positive plasmid and its concentration was measured. A gradient dilution of 5 × 102–5 × 108 copies/μL of the plasmid was used as template for quantitation test. By plotting the cycle threshold (CT) values against the copies of the plasmid, the standard curve was generated.