In order to make full use of yak milk resources， using yak milk casein as the raw material， the response surface analysis method was adopted to determine the optimal acylation conditions of yak milk casein and prepare high-quality and good bioavailability ferrous succinylprotein products. The structure of the products was characterized by means of Fourier transform infrared spectroscopy， particle size distribution， scanning electron microscopy， amino acid composition， and in vitro simulated digestion. The results showed that the optimal acylation process parameters of yak milk casein were as follows: The mass ratio of casein to succinic anhydride was 2∶1， succinic anhydride was added five times， pH value was 9， the reaction temperature was 48 ℃， the reaction time was 50 min. Under these conditions， the acylation rate reached 93.27%， the iron content was 8%， and the chelation rate was 93.03%. The determination results of Fourier transform infrared spectroscopy showed that there were differences in the absorption peaks between ferrous succinylprotein and casein， and the iron ions in the acylated protein formed coordination bonds with carboxyl groups and amino groups. The particle size of ferrous succinylprotein was measured to be larger by the laser particle size distribution analyzer， confirming the formation of the chelate. The analysis by scanning electron microscope indicated that the surface of the sample was smooth and the structure was compact. By determining the protein content and amino acid composition of ferrous succinylprotein， the results showed that the protein loss of ferrous succinylprotein compared to casein was 28.12%. Among them， Glu， Asp， and Pro had the higher contents in casein and ferrous succinylprotein. Glu and Asp were the key amino acids for forming chelates， and the bioavailability was better than that of inorganic salts. The results of this study can provide a reference for the preparation and structural characterization of ferrous succinylprotein.