This paper innovatively designed a full-nutrition formula powder based on the physiological characteristics of sarcopenia in the elderly. According to the digestive features of the elderly, an in vitro simulation of the oral-gastric-intestinal digestion system was conducted to evaluate the digestive properties of the full-nutrition formula powder for the elderly. The experiment adjusted the pH value and enzyme activity (α-amylase, pepsin, trypsin) of the digestive fluid, and measured the protein content, solid content, fatty acid release kinetics, rheological properties and microstructure changes after simulated digestion. The results showed that the protein content of the formula powder decreased significantly during the simulated digestion process. After digestion in the stomach and intestinal stages, the digestion rate of the formula powder reached 97.22%. The solid content of the formula powder decreased significantly (about 50%) in the stomach stage, remained stable in the intestinal stage, and reached the lowest level. The release of fatty acids conformed to the first-order kinetic model, and the release rate increased significantly in the first 40 minutes of the simulated intestinal digestion stage. Rheological properties showed that the apparent viscosity gradually decreased with the progress of digestion, and particle size analysis indicated that macromolecular substances were effectively decomposed (P<0.05), demonstrating better digestive properties of the formula powder. Microscopic structure showed that macromolecular substances were gradually degraded, and lipids were mainly digested in the small intestine stage. The study revealed the effective digestion and absorption characteristics of the formula powder in the simulated gastrointestinal environment of the elderly, providing a scientific basis for the optimization of full-nutrition formula powder for the elderly.