The solution enthalpy and the excess entropy of Zr in αU have been calculated based on first principles calculations in order to achieve U-rich solubility curves for U-Zr phase diagram. The enthalpy and the excess entropy of the Zr atom corresponding to Zr-αU transforming from solution state into δUZr2 are 1.437 eV/Zr atom and 1.060 kB/Zr atom by using the SQS model, which are 1.420 eV/Zr atom and 0. 732 kB/Zr atom with the disorder structure for δUZr2. But based on the experimental data, the fitted solution enthalpy and excess entropy are -0.823±0.712 meV/Zr atom and 5.880±9.976 kB/Zr atom, respectively. Through comparing the theoretical calculations and the experimental fitting results, it is found that the effect of the vibrational entropy on solubility could not be ignored. This discrepancy between the theoretical results and the experimental data might be related to the fact that the positions of Zr in δUZr2 in the theoretical calculations are not well consistent with the specific structural parameters of the the experimental samples.