•The Ga-In eutectic melting plateau was realized for the first time for more than 80 h with the temperature change<1.5 mK.•The inflection point manner shows the best performance, and is recommend for Ga-In eutectic melting point determination.•The phase transition point temperature was determined to be (15.6479 ± 0.0009) °C, with reproducibility of less than 0.14 mK. In this paper, the experimental results for binary alloys of gallium with indium melting plateau realization are reported. The Ga-In eutectic plateaus can last for more than 80 h with a temperature change of less than 1.5 mK. Various methods were employed to accurately determine the phase transition point of the Ga-In eutectic. By calculation, the point of inflection (POI) manner shows the best performance and is recommended for the determination of the Ga-In eutectic phase transition point. By repeatedly realising Ga-In eutectic melting plateaus, the melting point temperature was determined to be 15.6479 °C, with a reproducibility of less than 0.14 mK. The corresponding realization uncertainty of Ga-In eutectic was also analyzed and was found to be 0.90 mK (k = 2). These results are consistent with those of previous studies within the associated uncertainties and will help better understand the phase diagram and the corresponding thermal properties of the Ga-In eutectic.