Microalgae are considered as a renewable natural resource that presents important potentialities to be valorized in several fields. This valorization must necessarily start with a thorough study of the biochemical composition of each species of algae. The objective of this study is to study the evolution of the biochemical composition according to the different stages of growth of three biomasses of microalgae (Fragilaria sp, Scenedesmus protuberans and Polytoma Papilatum) collected from Moroccan aquatic environments. Polytoma Papilatum and Scenedesmus protuberans show high protein 89.23±2.58% and 90.4±1.45% respectively and low lipid 2.4±0.23 and 1.63±0.2% and carbohydrate 8.08±1.25 and 8.19±1.07 respectively. On the other hand, Fragilaria sp has high value of carbohydrate 65.73±3.25% and low in protein and lipid with values of 33.16±1.76 and 1.28±0.29 respectively. The monitoring of the growth kinetics allows to differentiate three phases on the growth curve: latent phase, exponential growth phase, and stationary phase. Regarding the biochemical composition, the highest content of proteins, carbohydrates and lipids in relation to the harvested biomass reach its maximum at the stationary phase.