The formation behavior of SrxBa1−xNb2O6 (SBN) (x=0.4 and 0.6) was investigated by the normal solid-state reaction route using SrCO3, BaCO3, and Nb2O5 as the starting materials. The phase assemblage of the reaction products at different temperatures was identified by X-ray Guinier-Hägg camera film data and the unit cell dimensions of SrxBa1−xNb2O6 formed during reaction sequence were also precisely calculated based on film data. The results indicated that four intermediate phases, i.e. Ba5Nb4O15, Sr5Nb4O15, SrNb2O6 and BaNb2O6 were developed during the formation of SrxBa1−xNb2O6. SrxBa1−xNb2O6 formed by the reaction of SrNb2O6 and BaNb2O6, appeared at 900 °C, whose intensity subsequently increased with the increase of calcination temperature. SrxBa1−xNb2O6 was the only crystalline phase when the starting powder was calcined at 1100 °C for Sr0.4Ba0.6Nb2O6 composition and 1200 °C for Sr0.6Ba0.4Nb2O6 composition. It was also found that the lattice parameters of SrxBa1−xNb2O6 formed at different temperatures decreased with the increasing calcination temperature, implying that the solubility of SrxBa1−xNb2O6 changed and more Sr would be incorporated into SrxBa1−xNb2O6 with the increase of calcination temperature. Based on the above results, the corresponding formation mechanism of SrxBa1−xNb2O6 phase was modified.