Abstract In this study, multi‐source thermospheric observations and TIEGCM simulations were used to explore the latitudinal variations of thermospheric temperature and total mass density at equinoxes. At nighttime, temperature and density exhibit consistent latitudinal patterns, with higher values at high latitudes. However, during daytime, their latitudinal patterns become opposite—density peaks at mid‐low latitudes where temperature is relatively low. This difference between daytime temperature and density reflects the modulation of large‐scale meridional circulation on density under typical thermospheric conditions. Equatorward circulation accumulates lighter species at mid‐low latitudes, counteracting thermal expansion. At night, the pronounced latitudinal temperature gradient dominates the density distribution, with composition only partially offsetting thermal effects. During the day, solar heating reduces this temperature gradient, enabling composition effects to fully override thermal effects and reverse the expected density pattern. These results highlight the critical role of composition in governing the spatial structure of thermospheric density.