In order to obtain high-quality nano-diamond film, ANSYS software is used to simulate the temperature field on the matrix surface. The effects of hot wire number, hot wire distance and distance between the hot wire and the matrix on the temperature field of the matrix surface are simulated and further verified by experiments. The results show that the influences of the hot wire number and the hot wire distance on the temperature field of the matrix surface are not significant, so that just take the appropriate values in the practical application. When the distance between the hot wire and the matrix is less than 5 mm, the temperature field of the matrix surface is uneven and undulating. When the distance between the hot wire and the matrix is greater than 5 mm, the average temperature on the matrix surface decreases with the increase of the distance between the hot wire and the matrix, while the undulating temperature field on the matrix surface disappears and the distribution of the temperature field tends to be uniform. When the distance between the hot wire and the matrix is 7 mm, the temperature field on the matrix surface is the most uniform, and the deposited nano-diamond film has the highest purity, the lowest internal stress and the best quality.