NOVELTY - The system comprises a water tank for pretreating organic wastewater by hydrolytic acidification, a photobioreactor having an intermediate connection unit, a pipeline, a constant flow pump, a one-way valve, and a liquid flow meter. The water tank comprises a tank body. The hydrolytic acidification takes place in the water tank using a gas flow meter. The organic waste water is stored in the water tank after pretreatment. The waste water is passed to the constant flow pump through the pipeline. The system further comprises a pH probe, and a temperature control jacket.    USE - The system is useful for culturing microalgae in waste water (claimed).    ADVANTAGE - The system cultures the microalgae in an economical and energy-efficient manner.    DETAILED DESCRIPTION - The system comprises a water tank for pretreating organic wastewater by hydrolytic acidification, a photobioreactor having an intermediate connection unit, a pipeline, a constant flow pump, a one-way valve, and a liquid flow meter. The water tank comprises a tank body. The hydrolytic acidification takes place in the water tank using a gas flow meter. The organic waste water is stored in the water tank after pretreatment. The waste water is passed to the constant flow pump through the pipeline. The system further comprises a pH probe, a temperature control jacket, a continuous stir reactor, a fixed bed biological membrane, an up flow anaerobic sludge blanket reactor and a sterilizing unit. The hydrolytic acidification process comprises adding an activated sludge to the waste water, fermenting the mixture, filtering the mixture to obtain filtrate, sterilizing the filtrate using the sterilizing unit, adding PVC and polybutylene terephthalate to the sterilized filtrate, and discharging the precipitated sludge through a discharge tank. The tank body is connected with a water inlet. A middle portion of the tank body is connected with an air pump. The temperature control jacket is connected to a light source comprising incandescent lamp, LED, and halogen lamp. The constant flow pump prevents the pipeline from blockage. The sterilizing unit has a closed structure. The sterilization process comprises high temperature sterilization and ultraviolet sterilization, and is carried out for 30-60 minutes.