Organic and inorganic substances which were released into the environment as a result of domestic, agricultural and industrial water activities lead to organic and inorganic pollution. The normal primary and secondary treatment processes of these wastewaters have been introduced in a growing number of places, in order to eliminate the easily settled materials and to oxidize the organic material present in wastewater. The final result is a clear, apparently clean effluent which is discharged into natural water bodies. Treatments of wastewater with Microalgae based system have the ability to remove nutrients. (Nitrogen, Phosphorus and other nutrients), BOD, COD and other impurities present in the wastewater by using the sunlight, CO2, and impurities like nutrients present in the wastewater. The microalgae also have the ability to fix the excess. Carbon dioxide presents in the environment and release the oxygen and solve the problem of Global warming. According to the various study, the nutrients removal efficiency of microalgae based wastewater treatment system is very high as it removes 78-99% of Nitrogen and Phosphorus. Microalgae culture offers an interesting step for wastewater treatments because they provide a tertiary bio treatment coupled with the production of potentially valuable biomass, which can be used for several purposes. And also, for their capacity to remove heavy metals, as well some toxic organic compounds, therefore, it does not lead to secondary pollution. In the research, we will highlight on the role of micro-algae in the treatment of wastewater.