The thermal quenching property of phosphors has been proven to have a strong impact on the application of them. In this paper, a series of (Ba1−xSrx)2SiO4:Eu2+ compounds have been synthesized via conventional high-temperature solid-state reaction. Based on the Rietveld fitting analysis of the X-ray diffraction data, the preferential occupancy behavior of Sr2+/Ba2+ ions is verified. We adopt the cation ordering to characterize this preferential occupancy and find that the degree of cation ordering reaches its maximum at x=0.5 and decreases as x deviates from 0.5. The photoluminescence measurements show that the intermediate composition (x=0.5) exhibits the best luminescence thermal stability with T1/2 over 200 °C. The composition dependence of thermal quenching temperature is well similar to the composition dependence of the degree of cation ordering, indicating that the thermal quenching property of (Ba1−xSrx)2SiO4:Eu2+ is positively related to the cation ordering. This work provides a deeper understanding between thermal quenching properties and crystal structures of phosphors.