Freshwater microalgae that contained high starch, carbohydrates and lipids contents are beneficial to human being in many industrial especially in food and food packing industries. There are a few freshwater microalgae that contained high starch and carbohydrates content such as Chlorella vulgaris, Chlorella emersonii, Chlorella sorokiniana, Nannochloropsis salina and Spirulina sp. Spirulina sp. is chosen in this research because of its strong adaptation to the environment changes, short life cycle and able to produce high intracellular starch. In this project, results have shown that microalgae at late exponential phase contained the highest starch and carbohydrate yield of 0.491±0.046 mg/L and 0.090±0.046 mg/L, respectively. Thus, the harvesting time for microalgae with high starch production and yield is phase dependent rather than time dependent. Under optimized cultivation conditions of aeration at 5 L/min, using white wavelength and 32ºC, Spirulina sp. produced the highest starch and carbohydrate yield of 0.664±0.03 mg/L, and 1.019±0.025 mg/L, respectively. In conclusion, compared to before optimization, starch and carbohydrate yield after optimizations were increased. In conclusion, compared to before optimization, starch and carbohydrate yield after optimization were 435% and 221% increased, respectively.