The invention discloses a ball-in-ball machining fixture and a utilization method thereof. The fixture comprises an index plate, a positioning plate, a front vertical supporting plate, a supporting plate, an adjustable supporting seat, a bottom plate, a centre seat, a live centre, a fixing plate, a rear vertical supporting plate and a taper shank positioning seat. The index plate which is a disc is mounted on the taper shank positioning seat through a rotating shaft and capable of rotating around the rotating shaft by 360 degrees; 20 positioning holes are uniformly and annularly distributed in the index plate; the positioning plate is a sector plate, and five positioning holes are uniformly distributed in the positioning plate along an arc line. The ball-in-ball machining fixture has advantages that firstly, marking of lines and points on the surface of a ball is avoided; secondly, repeated correction of a relative position of a tool to drilling points on the surface of the ball in machining of each hole is avoided; thirdly, machining and manufacturing efficiency is improved, and errors of manual correction and positioning are avoided; fourthly, simplicity in operation, structural stability, accuracy in positioning and convenience in demounting and transporting are realized. Ball-in-ball rotation angles are positioned by cooperation of the live centre and the index plate, and accordingly precision of drilling positions is guaranteed.