The three microalgal proteins - Spirulina platensis protein(SPP)， Chlorella pyrenoidosa protein (CPP)， and Nannochloropsis oculata protein (NOP) were isolated， and their emulsifying properties and interfacial characteristics were examined across pH values of 1， 3， 5， 7， and 9. Emphasis was placed on comparing and evaluating the stability， rheology， and morphology of DHA algal oil emulsions that were stabilized by SPP， CPP， and NOP. Results indicated that near their respective isoelectric points (pH 3)， minimal solubility， emulsifying activity， emulsion stability， and maximal hydrophobicity were exhibited by SPP， CPP， and NOP. Higher solubility and emulsion stability were shown by NOP and SPP compared to CPP， whereas superior emulsifying activity， especially for NOP， was exhibited by NOP and CPP. Nanoemulsions were prepared by sonication， using pH 7 microalgal protein solutions as the continuous phase and 10% DHA algal oil as the dispersed phase， revealing a distinct water-in-oil structure observed via microscopic and SEM imaging. Successful encapsulation of DHA algal oil within all three microalgal proteins was confirmed by XRD and FTIR， with DSC and TGA results demonstrating good thermal stability. Among them， NOP-stabilized emulsions exhibited the smallest average particle size， most uniform dispersion， superior rheological properties， apparent viscosity， and storage stability compared to CPP and SPP， indicating potential applications as high-quality plant protein emulsifiers.