The work is conducted to uncover and simulate the dependence of the evolving anisotropic-asymmetric yield behavior on the temperature for an Mg-Gd-Y alloy. Experiments were carried out at 25~300 ℃, including uniaxial tension and compression. The strength is observed to decrease non-linearly as the temperature increases. Thermal softening effect is not significant when the temperature is lower than 200 ℃, but the strength decreases dramatically at high temperature than 250 ℃. Tension-compression asymmetry and anisotropy are observed to be strongly and nonlinearly dependent on strain and temperature. The temperature effect is taken into account in a combined Swift-Voce (SVT) model to predict the temperature-dependent strain hardening behavior with a higher accuracy than the traditional Johnson-Cook and Zerilli-Armstrong equations. An analytical Yoon2014 (A-Yoon2014) yield function is established to capture the evolving anisotropic-asymmetric behavior with respect to strain and temperature. The predicted force-stroke curves of the A-Yoon2014+SVT model are closer to the experimental results of the three-point bending process than the numerical results of the original Yoon2014+SVT model. Given its user-friendliness and high accuracy for the modeling of temperature-dependent anisotropic-asymmetric hardening behavior, the A-Yoon2014+SVT model is recommended to be utilized in the numerical simulation of plastic forming process for hexagonal close-packed metals.