Emulsions form a major basis of various processed food products. Due to their surface-active property, food proteins, especially the plant proteins that are gaining increasing popularity recently, are important emulsifiers to form and stabilize emulsions. Proteins contribute to a stable emulsion by forming a protective layer at the oil-water interface thus to lower the interfacial tension and provide the electrostatic and structural barrier. The demand for developing more food emulsion-based products to meet customers’ sensorial preferences necessitates the characterization of protein emulsification properties. This chapter delineates three commonly applied methods to characterize protein emulsification ability, namely, the centrifugation method, the turbidimetry method, and the conductivity method. These methods vary in different principles and give diverse indices that underline protein emulsification mechanisms, i.e., emulsion activity (EA), emulsion stability (ES), emulsion activity index (EAI), emulsion stability index (ESI), and emulsion capacity (EC). The detailed protocols and information overviewed in this chapter provide important insights in choosing appropriate proteins to advance the development of food emulsion-based products.