The invention relates to the technical field of functional beverages, and especially relates to a functional spirulina protein peptide beverage capable of improving immunity and sleep quality. The beverage can be directly drunk, tastes sour and sweet, does not have alga smell, is convenient to carry, solves the tedious problem that traditional foods need to be brewed for being eaten, and has the effects of regulating the immunity and improving the sleep quality. The beverage comprises, by weight, 5-7% of spirulina protein peptides, 3-5% of fructo-oligosaccharide, 3-5% of passion fruit concentrated juice powder, 2-4% of erythritol, 1-3% of sweet orange concentrated juice powder, 0.8-1.2% of citric acid monohydrate, 0.2-0.4% of DL-malic acid, 0.1-0.3% of sodium carboxymethyl cellulose, 0.2-0.4% of pectin, 0.2% of gamma-aminobutyric acid, 0.1% of sodium citrate, 0.01-0.03% of xanthan gum, 0.01-0.02% of sucralose and 73-84% of water. Main functional components of the spirulina protein peptide beverage are the spirulina protein peptides and gamma-aminobutyric acid, small molecule peptides are easier to absorb by human bodies, and the spirulina protein peptide beverage is free of sucrose, essence, pigment and preservative, and is suitable for middle-aged and elderly people and diabetic patients to drink.