Thermal contact resistance, a parameter that describes the thermal transferability of the interface between the melt and the metallic wall, exercises a significant influence on the surface quality of the resulting part, especially in thin wall injection molding. In this study, temperature data of the melt was quantitatively measured with only 2 micro thermocouples, and TCR of specimens with 4 kinds of thickness was calculated after data processing with a new mathematical model. It was demonstrated that TCR was deeply affected by mold temperature. When the mold temperature increased from 90 degrees C to 130 degrees C, the rate of TCR decline was 56.72%. Melt cooling simulation was performed with different values of TCR, which played the dominant role of TCR in calculating the temperature distribution in thin-wall injection molding. It showed that TCR exercises a significant influence on the simulation of the cooling rate, and the influence cannot be ignored, especially in thin-wall injection molding.