The annual yield of Spirulina (Arthrospira) in China is approximately 10,000 tonnes, accounting for 60-70% of the total capacity in the world. As the largest Spirulina production base in China, Ordos Spirulina Industrial Park in Inner Mongolia plays an important role in the Spirulina industry. Yet, to date little is known about the dynamic changes of Spirulina under real production in this region. Therefore, the growth, quality, and nutrients consumption of Spirulina in diel cycle and semi-continuous culture mode under commercial production scale were investigated and analyzed to help optimization and management of production. Significant variations in biomass, photosynthetic activity, and biochemical components were observed during the diel cycle. Biomass increased during the daytime and decreased at night, losing 22% of what had been accumulated in the daytime. The change of carbohydrate content was consistent with that of biomass. The photosynthetic pigments declined obviously at midday due to the much higher light intensity and dissolved oxygen (DO), and always recovered at night. Under the semi-continuous culture mode, a biomass productivity of 11.2 g m(-2) day(-1) was obtained. The change of nitrogen and phosphorus concentration in the medium indicated that the nutrients supply was imbalanced, and the phosphorus was quite possibly excessive in this mass culture. It is recommended that the supply of phosphorus can be decreased to one-third of the original concentration without harmful effect on growth and quality of Spirulina. The present study may deepen our understanding of Spirulina production on a commercial scale and provide the guidance for cost-effective production of Spirulina in this region.