In this paper, by collecting and summarizing the reported overall composition and phase composition of 18 eutectic high-entropy alloys (EHEAs), some parameters reflecting their properties were calculated, including mixing enthalpy, mixing entropy, Gibbs free energy, atomic size mismatch, the electronegativity difference and the valence electron concentration , and the influence of these parameters on the structure of the alloy were analyzed from a thermodynamic point of view. It is found that the calculated mixed entropy equivalent of the overall composition of the eutectic high-entropy alloy basically meets the structural criterion requirements of the traditional high-entropy alloy to form a single-phase solid solution. (Such as △Smix >11 J/(mol·K)、-15 kJ/mol < △Hmix < 5 kJ/mol、δ < 6.6%) But because the average free energy of the eutectic phase is lower than the total free energy when the whole forms a single phase, this makes the eutectic high-entropy alloy in the solidification process A eutectic reaction occurs, forming a multi-phase structure.