Optimal vaccination against circulating IBV strains in China requires the development of attenuated vaccines designed from local strains [20], [21], [22], [45]. However, due to the particularity of RNA virus replication, attenuated vaccine strains generated by continuous passage remain associated with the risk of reversion to virulence or potential recombination between vaccine strains and virulent field strains [27], [46], [47], which represents a substantial hidden concern to the poultry industry. To reduce the problems associated with vaccine reversion, researchers have explored the option of creating vaccine viruses using reverse genetic technology (e.g., Beaudette strains carrying the S1 gene of the H120 vaccine strain, virulent M41 strain, or QX-like strain) [30], [48]. However, the titer of the Beaudette strains carrying the S1 gene of the vaccine H120 strain only reaches 106.13 ± 0.23 EID50 [49], which is lower than that of the H120 backbone strain. Therefore, we aimed to develop a recombinant rH120-S1/YZ strain based on the H120 vaccine strain that carries the S1 gene of the ck/CH/IBYZ/2011 strain (a Chinese QX-like nephoropathogenic strain) using reverse genetic technology [35], [36].