Casein is a common ingredient and can be used to improve the stability of dairy products. However, the poor solubility and emulsification properties of casein limit its further application. Therefore, modification of casein to improve its application properties is important. In this study, hydrolysis and succinylation were used to modify the casein separated with different methods (rennet casein (RC) and membrane separated casein (MC)). And Turbiscan stability index (TSI), salt ion (Na+) stability, freeze-thaw stability and storage stability of emulsions prepared by RC and MC were investigated. The results showed that succinylation modified protein structure and improved the stability of oil-in-water emulsions prepared by succinylated casein and succinylated casein hydrolysates. The TSI of succinylated rennet casein (RC-SA) and succinylation of membrane separated casein hydrolysates (MC-CHs-SA) stabilized emulsions showed a better stability. Protein succinylation could prevent adsorption and aggregation between droplets, improving the Na+ stability and storage stability of the emulsion. Succinylated casein had the best emulsification activity and emulsion stability. And the solubility of succinylated casein hydrolysates was significantly improved compared with succinylated casein. Emulsions prepared with succinylated RC hydrolysates had the smallest particle size and a more uniform particle size distribution compared with other samples. Succinylated MC hydrolyzates showed the best freeze-thaw stability. Therefore, hydrolysis could reduce the molecular weight of casein and significantly improved the solubility of succinylated casein, and succinylation could modify the protein structure and significantly improved the emulsion stability. Overall, hydrolysis and succinylation can be applied to modify casein to effectively improve the application properties in emulsion system.