The invention discloses a diamond finishing nib center distance precision detection method and an apparatus thereof. An intermittent rotating mechanism is used to drive a diamond finishing pen to rotate a circle intermittently. An image sensor which directly faces a diamond nib collects a plurality of images during a diamond finishing pen rotation process. Through image synthesis, a diamond nib rotation track is displayed, a diamond nib rotation radius is determined and a diamond finishing nib center distance is acquired. Detection efficiency is high and a detection effect is good. In the invention, a diamond finishing pen quality detection system is improved, which is good for advanced manufacturing-technology rapid development; a precision and ultra-precision processing technology is promoted to develop; and grinding processing precision and surface quality are increased.