The invention relates to a diagonal hole drilling mold for a nozzle ring of an engine. The diagonal hole drilling mold comprises a base, supports, a positioner, a mandrel, a bearing, a tangential clamping cover, a bearing cap, an indexing plate and the like. The left and right supports are fixed to the base through pins and bolts, the bearing is mounted in center holes in the upper ends of the left and right supports, the mandrel is connected with a positioning plate through the pins and the bolts and is placed in bearing holes at two ends separately, the bearing cap is located at the upper end of a bracket, the tangential clamping cover is located between the bearing cap and the bearing, and one end of the tangential clamping cover is connected with a handle nut. The mandrel is locked during work. The indexing plate is connected with a lug at the left side of the positioning plate through the pins and the bolts, and a special angle is formed between the indexing plate and the lug. When a drilling mold works, a diagonal hole is processed from the front face and the back face by positioning the drilling mold through positioning holes in two ends of the indexing plate position. Positioning rings and the positioning plate are connected through the pins and the bolts, and the positioning is achieved by the cooperation of an excircle and an inner hole of the nozzle ring. The diagonal hole drilling mold has the advantages of being high in positioning precision, convenient to operate, high in practicality and the like, and can be used for processing complex diagonal holes.