A continuous culture of Spirulina (Arthrospira platensis) was performed for 78 in a tubular photobioreactor of 300 L volume. During this period there was growth in biomass and crop response to the strategy of adding the nutrient medium. Using as a basis the modified Zarrouk medium, three nutritive combinations were elaborated: initial medium (MI), growth medium (SA1+SA2) and maintenance medium (SB1+SB2) for different crop stages. The media delivery is affected gradually and in accordance with requirements of growing biomass (dry weight) daily cultivation. The initial crop biomass was 2.0 g L-1, on day 20 of culture was made the first partial harvest (50%) starting a new stage of the crop with an initial biomass of 1.7 g L-1, 20 days after a second crop was partially culture initiating a third culture step with a biomass of 1.6 g L-1. The results obtained after harvest were, on the average, 3.7; 4.1 and 9.7 g L-1 respectively. The proximal analysis was performed at the end of the continuous cultivation showed a 71.6% of protein content.