The invention discloses a high-precision deep hole combination drill which comprises a cutter handle, a blind rivet and a straight fluted drill. The front end of the blind rivet is inserted into a connecting hole in the right end of the cutter handle, and the straight fluted drill is inserted into a mounting hole formed in the left end of the cutter handle and is fixed by a compression screw and a compression groove. The invention further discloses a machining method of the high-precision deep hole combination drill. The machining method specifically comprises the steps of cutter handle machining, straight fluted drill finish machining, cutter handle finish machining, boundary dimension finish machining and dynamic balancing. The combination drill machined through the machining method has the advantages of being high in fatigue durability, high in strength, high in precision, resistant to abrasion, high in chip removal and cooling capacity, high in machining precision and the like, and the number of defective products or waste products can be greatly reduced.