Abstract Adding high thermal conductive fillers to base materials has been recognized as an efficient way to increase the thermal conductivity of composites materials. The heat conductive path is formed by filler contacts, this is a key point. In this paper, the effects of filler contacts are investigated based on generalized model and isolated model. The results indicate that the thermal conductivity is always linearly increased with the sphere filler contents. However, for cube filler, when the volume content exceeds 10%, the growth of thermal conductivity is accelerated along with filler contents. The 10% filler content is the inflection point and percolation threshold for cube filler. It is much lower than previously reported. The effect of filler contacts is very small for sphere fillers. Meanwhile, the deviation of thermal conductivity between two-dimensional and three-dimensional model is also very small for sphere filler. The cube fillers have substantial effects on the consequently thermal conductivity than sphere fillers. A series of new three-dimensional generalized model are proposed by numerical method. The filler contacts are considered in this model, the deviation with the experiment tested is in an acceptable range at wide filler contents.