Thermal contact resistance plays an important role in many domains, such as microelectronics and nuclear reactors. This paper proposes a more comprehensive model for the prediction of constriction resistance of rough contact between nominally flat surfaces in vacuum. Firstly, a 3D geometrical asperity contact model is proposed based on the analysis of the profile of actual engineering surface. In this model, the contact is not simplified as a rough surface contacting with a perfectly smooth surface, but described as two rough surfaces. Oblique contact is considered and the effects of several parameters such as the shape of the asperity, the depth of interference, and the radial distance between the centerlines of the contacting asperities are investigated. Some mathematical derivations for constriction resistance are performed, and a series of numerical simulations are also carried out, covering a wide range of values of these parameters in practice applications. A comprehensive correlation for constriction resistance as a function of these parameters is finally obtained by nonlinear curve fitting, and it is validated through some comparisons and it can be used to predict more accurately the thermal contact resistance between rough surfaces.