High-entropy carbides have been widely studied as a new type of solid solution due to their unique properties. However, their solid solution mechanism in sintering is still not understood. In this work, partially dense inhomogeneous (ZrTiTaV)C ceramics are prepared by different sintering processes, and their mechanical and thermal properties are investigated. From composition characteristics of Zr-poor and Ta-rich in the dense area, it is known that the (TiTaV)C ternary solid solution is preferentially formed and densified, while the diffusion of zirconium atoms requires higher energy during the sintering process of (ZrTiTaV)C. Moreover, density functional theory (DFT) calculations reveal that the critical formation temperature of (TiTaV)C solid solutions is lower than that of (ZrTiTaV)C, which confirms the reasonableness of the experimental results. Overall, our work sheds light on the solid solution sequence and solid solution mechanism in sintering of (ZrTiTaV)C, and also provides a route to prepare high-entropy carbides with uniform composition.