The invention relates to a manufacturing method of large-size C-oriented 
sapphire crystals. According to the method, an 
alumina raw material with the high purity of 99.999 wt% is adopted and is heated to be molten and subjected to 
crystal seeding and 
crystal growing. A main heater and an assistant heater are adopted, wherein a 
tungsten rod cylinder-shaped heating body is arranged around a 
crucible and is used as the main heater; another 
tungsten disc-shaped heating body is arranged at the bottom of the 
crucible and is be used as the assistant heater; the 
power ratio of the main heater to the assistant heater is (20 to 80 KW): (10 to 60 KW). In addition, a 
tungsten tube is mounted at the top of the 
crucible, and 
argon is introduced into the tungsten tube to regulate the temperature of the 
seed crystal and a liquid surface. As the method is used, the temperature distribution of a longitudinal temperature field in the crucible is improved, so that air bubbles, cracks and other defects are avoided or reduced, i.e., the 
seed crystal is prevented from being molten at overhigh temperature during the 
crystal seeding process. Therefore, the generation of a C-oriented long crystal boundary with a small angle is controlled effectively. As a result, the growing C-oriented crystals with the 
diameter of 14 inches are good in position staggering density and 
single crystal performance. Consequently, the method provided by the invention reaches the international advanced level.