Objective To investigate the expression of HA1 gene of avian influe nza virus (AIV) subtype H7N2, which can be used for detection of antibodies to H 7 subtype AIV, and for further study of HA1 protein function. Method The gene of H7N2 subtype AIV was amplified by RT-PCR and cloned into pGEM -T-easy vecto r. The HA1 gene expressing plasmids was constructed by inserting the target g ene fragments into pCEX-4T-2 vectors. The proteins expression was induced by IPTG and analyzed by Western blot. An indirect ELISA method was established as to de tect the expression of HA1 fusion protein. Positive sera of H5, H7, H9 subtype A IV were detected by this indirect ELISA. Results HA1 gene of H7 N2 subtype AIV was s uccessfully cloned and sequenced. This gene encoded 322 amino acids. The constru cted HA1 gene expressing plasmids was transformed into E. Coli BL21 competen t ce lls, and the HA1 fusion protein with molecular weight of 61kD was expressed. The expressed HA1 fusion protein showed a positive reaction with H7N2 subtype AIV p ositive serum, and a negative reaction with H5 and H9 subtype AIV positive serum . Conclusion The HA1 gene of H7N2 subtype AIV was expressed in E. Coli BL21. T he expressed HA1 fusion protein shared a positive reaction with H7 subtype AIV p ositive serum, and a negative reaction with H5 and H9 subtype AIV positive serum .