The model of the diamond coating at the film-substrate interface is established by using the molecular dynamic method. The interaction between the atoms in this model is described by the Morse potential function and Tersoff potential function. Based on the above, we carry out the molecular dynamic simulation of the mechanical properties of the model in a temperature range from 0 to 800 K. The simulation results show that the tensile strength of diamond coating at the film-substrate interface presents a downward trend as the temperature rises from 0 to 800 K: the downward trend is evident when the temperature is in a range of 0-300 K, and the downward trend is smooth when the temperature is in a range of 300-800 K. Meanwhile, the variation of system energy with temperature presents a downward trend similar to the variation trend of the tensile strength.