Diamond thin films were fabricated using a custom-made multinozzle oxy-acetylene flame apparatus. These films were characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. Experimental results show that this multinozzle combustion flame technique can produce high quality diamond films, as judged by Raman spectroscopy, with relatively large deposition areas. The surface morphology, crystal structure and optical properties of these films are found to be greatly affected by processing parameters, such as substrate temperature, gas ratio of acetylene to oxygen, and the configuration of the multinozzle. Compared with the single-nozzle oxy-acetylene flame technique, this multinozzle method has greater potential for obtaining large-area diamond film coatings. However, more engineering design and investigation are needed. The uniformity of these films and the relationship between the deposition conditions and their properties are discussed.