The invention discloses a double-layer orifice oil atomizer of a diesel engine. Alternated oil spraying of two layers of spray holes can be achieved. Two layers of lateral spray holes distributed in a staggered manner are formed in an injection nozzle at the lower portion of a needle valve body. Armatures above an oil atomizer body control a needle valve rod to move upwards through throttling holes below the oil atomizer body, the spray holes in the lower layer of the injection nozzle spray oil, and a needle valve rod downward moving armature control body is arranged on the outer side of the upper portion of the oil atomizer body. An armature in the needle valve rod downward moving armature control body can control downward moving of the needle valve rod through throttling holes below the armature, and the spray holes in the upper layer of the injection nozzle spray oil. According to the oil atomizer, the two-time atomizing space changes in the secondary injection process can be achieved, the fuel space atomization can be better utilized, diesel atomization is even, and the particle emission of the diesel engine is reduced. Due to the fact that two sets of spray holes are utilized for spraying oil, two control cavities control upward moving and downward moving of the needle valve rod respectively, and the time interval between two times of injection can be controlled within the narrow range.