Thermal contact resistance is a key bottleneck to restrict the rapid heat dissipation of electronic device. The wetting between two contact surfaces is one of the most important factors affecting the thermal contact resistance. Phase change thermal interface material can transform from solid state to molten state by heat inducing, which is an efficient way to reduce the thermal contact resistance. In this work, a novel form stable phase change thermal interface material of graphene/olefin block copolymer/paraffin filled with graphene (≤4.0 wt%) was designed. Furthermore, the influence of temperature and pressure on thermal contact resistance were studied, and the dominant position of thermal contact resistance and RTIMs in total thermal resistance was analyzed systematically. The results exhibit that thermal contact resistance decreases sharply from 8–20 Kcm2/W to 0.1–0.2 Kcm2/W for the temperature increases from 37 °C to 45 °C (50 Psi), with a drop of up to two orders of magnitude. This is because the wettability of the two contact surfaces is greatly improved by changing solid–liquid contact to solid–liquid contact. In addition, the thermal contact resistance decreases slightly with the increase of pressure (10–50 Psi, 48 °C). A small amount of graphene can significantly enhance the thermal conductivity of graphene/olefin block copolymer/paraffin, but the effect on thermal contact resistance is relatively weak. Moreover, critical thickness is proposed to quantitatively evaluate the dominant position of thermal contact resistance or RTIMs in total thermal resistance. It facilitates the quantitative analysis and optimization of thermal resistance in practical application.