The growth process of rutile single crystal was studied by numerical control flame melting crystal growing furnace and three-tube burner. It is shown that internal oxygen was the basis of the three gas parameters. When the internal oxygen flow was less than the characteristic value Oin(min) of 6.6 L/mm or greater than the characteristic value (Oin(max) of 7.1L/mm, the crystal growth was prone to melt flow or not easy to expand, and the growth process was forced to stop, so the crystal was difficult to grow into large-size crystals. When the internal oxygen flow was larger than 6.6 L/mm and smaller than 7.1 L/mm, the growth process was stable and could grow into large-size crystals. When the internal oxygen flow was 7 L/mm, rutile single crystal with a diameter of 30 mm and a length of 45 mm was grown. The composition, structure and bond structure of the crystal were characterized by energy spectrometer, X-ray diffraction (XRD) and Raman spectrometer, indicating that the crystal was a typical single crystal of rutile, and the growth direction was [110]. [ABSTRACT FROM AUTHOR]