Objective To optimize the extraction process of spirulina protein isolate and analyze its physicochemical and functional properties.Methods The extraction process was optimized using single-factor test and orthogonal test, with the extraction yield of spirulina protein isolate as the evaluation index. Comprehensive comparisons and analyses were conducted on the physicochemical properties, structural characteristics, and functional properties of spirulina protein isolate.Results The optimal extraction conditions for spirulina protein isolate using alkaline dissolution and acid precipitation were as follows: solid-liquid ratio of 1∶20 (g/mL), extraction time of 1 h, pH value of 8.0, and extraction temperature of 40 ℃. Under these conditions, the yield of spirulina protein isolate reached 280.36 mg/g. The obtained spirulina protein isolate exhibited a dark green appearance, with a surface hydrophobicity of 330.49, a free sulfhydryl group content of 20.51 μmol/g, and a relative molecular mass of 1.8×10⁴. Compared with soybean protein isolate, peanut protein isolate, and egg white protein, it demonstrated superior foaming and emulsifying abilities.Conclusion Spirulina protein isolate is a natural plant-based protein with relatively favorable functional properties and holds promising prospects for development and utilization.