The invention discloses a production method of a foodstuff which is a boxed dietary fish product, and belongs to the technical field of aquatic product processing. According to the invention, hairtail or small yellow croaker is adopted as a raw material, and the boxed dietary fish product is obtained through the processing steps of selecting, pre-treating, washing, salting, frying, weighing, flavoring liquid adding, membrane sealing, sterilizing, temperature-preserving, packaging, and storing. The obtained foodstuff which is the boxed dietary instant fish product is advantaged in unique and good appearance, convenient unsealing, delicious taste, and high safety. The foodstuff is suitable for family dishes, hotels, and field trips. According to the invention, membrane sealing and packaging are carried out by using special foodstuff boxes, and the sterilizing conditions are relatively mild, such that loss and waste during the processing process are reduced, a yield is ensured, and high-efficiency and low-loss production of the advantaged instant fish product are realized. The production process is simple and environment-friendly, such that real continuous clean production can be realized. The product can satisfy the requirements by the current market for high-grade instant dietary marine products, and provides good production demand and economical benefit.