Spirulina (scientific name Arthrospira platensis or Spirulina platensis) contains 60 - 70% protein, 13 - 16% carbohydrate, 7 - 8% lipid, many essential amino acids (lysine, methionine, phenylalanine, tryptophan...), vitamins (E, B6, B12...), and minerals (Cu, Zn, Mg, K, Fe...). Currently, Spirulina is widely applied in many areas of life; making functional foods, essential nutritional supplements, medicines, cosmetics, animal feed and wastewater treatment. The research was carried out with the goal of exploiting the native gene source of microalgae distributed in Kim Boi hot spring – Hoa Binh, thereby selecting algae strains with high yield and good quality. The results indicated that in 5 medium Hoagland, BBM, ½ Chu-10, BG11 and Zarrouk, 3 strains of Spirulina sp. were isolated and grow well on BBM and Zarrouk medium. Among the 3 strains of Spirulina, two strains KB1 and KB2 have been identified with the potential to breed for research and production on an industrial scale. The strain KB1 created 0.5 g of dry biomass per liter of culture fluid, the protein content was 74.5 g/100 g of dried algae. The strain KB2 had a yield of 0.45 g of dry biomass per liter, and the protein content was 75.3 g/100 g dry biomass.