Abstract: The high-quality GaN thin films were prepared on graphite substrate by ECR-PEMOCVD technique with low-temperature deposition.In this study, the trimethylgallium(TMGa) and nitrogen(N₂) were used as reaction sources for preparing GaN as-grown films.The properties of GaN film at different preparation temperatures were systematically studied using X-ray diffraction analysis, electron scanning microscopy, and room temperature photoemission spectroscopy test systems.The results show that the dense uniform GaN films with high C-axis orientation are deposited successfully on the graphite substrate at a deposition temperature of 450℃.And the band-edge ultraviolet emission peak is dominant, which indicates excellent optical properties of the as-grown GaN films.