The invention relates to an octafluoropropane purifying method and a purifying apparatus thereof, which belong to the field of fine chemical engineering. The purifying method employs a cold trap for light-discharge and heavy-removal processing of an octafluoropropane crude product, the light components and heavy components impurity content are greatly reduced; an adsorbent is used for adsorption, H2O content is reduced, a part of a fluorocarbon compound is absorbed; a rectification technology is employed, the high-boiling point and low-boiling point impurity can be removed by controlling the rectification parameters, the H2O content is less than 1 ppm, the content of the organic fluorocarbon compound is less than 1 ppm, the total impurity content is less than 10 ppm, cold amount and heat consumed during the rectification process are reduced, economic performance is good, and the octafluoropropane with purity of greater than 99.999% can be obtained after being purified. The purifying apparatus mainly comprises the cold trap, an adsorption tower and a rectifying tower, and is adapted to usage of the purifying method.