The invention relates to a method and an apparatus for high pressure gas phase preparation of boron nitride spherical powder. According to the present invention, an easily-evaporated or easily-decomposed substance containing boron and nitrogen is used as a reaction precursor, the solid or liquid of the substance is sealed in a reaction apparatus, the reaction apparatus is placed in a suitable heating furnace, heating is performed at a suitable temperature in a protective atmosphere to make the precursor be evaporated or decomposed to produce a high pressure, and boron nitride spheres are successfully prepared under the action of the high pressure; the used reaction apparatus comprises a reaction chamber, a sealing ring and a fastening screw; the method has advantages of simple process, low cost, low synthesis temperature, short time and high yield (more than 99%), and can prepare a lot of boron nitride spheres; and the obtained boron nitride spheres have characteristics of low specific surface area (1.12 m<2>/g) and high oxidation resistance, and have the oxidation initiation temperature of 895 DEG C, such that the boron nitride spheres can have good application prospects in lubricants, polymers and ceramic composite materials.