The invention provides a device for cultivating microalgae in wastewater and a production method thereof. The production method comprises the following steps: preparing a hollow adsorption column assembled by adsorption films by utilizing modified chitosan and modified montmorillonite to adsorb metal ions in the wastewater, enabling the wastewater to penetrate through the adsorption column under a pump negative pressure effect and stay in the adsorption column for contacting immobilized microalgae, wherein organic nutrients in the wastewater are utilized by the microalgae for growth and reproduction. By utilizing the method for wastewater treatment, substances such as the metal ions, carbon, nitrogen and phosphorus in the wastewater can be effectively removed, and meanwhile the microalgae can be cultivated on a large scale, so as to achieve the dual purposes of wastewater treatment and microalgae cultivation. The treated wastewater can be used for irrigation, breeding, cleaning and the like; and the cultivated microalgae can be used for aquaculture, feed addition, vegetable oil extraction and the like.