This paper presents a new water retention curve (WRC) model for the simulation of coupled thermo-hydro-mechanical processes in geological porous media. The model simultaneously considers the impact of porosity and temperature on suction, for both wetting processes and drying processes. The model is based on an idealization of porous geological media as having an isotropic and homogeneous microscopic pore structure. Suction is expressed as a function of degree of saturation, porosity, surface tension of the water-air interface, and the length of air bubble perimeter of the pores per unit area on a random 2D cross-section of the medium. The tension of water-air interface is written as a function of temperature, and the length of perimeter of the water-air interface of the pores becomes a function of porosity and degree of saturation. The final equation of the new WRC is a function of suction, effective degree of saturation, temperature, porosity, pore-gas pressure, and the rate of degree of saturation change with time for both wetting and drying processes. The model was used to fit experimental data of the FEBEX bentonite, with good agreements between measured and calculated results.