Abstract: Microalgae biofilm can effectively remove pollutants with low energy consumption and production costs in wastewater treatment. The formation of the microalgae biofilms can depend mainly on the adhesion properties of the attachment materials. The optimal attachment materials can greatly contribute to the wastewater treatment efficiency of the microalgae biofilm. Taking the simulated anaerobic digestate food waste effluent as the subject, this study aims to evaluate the adhesion, durability, and cost-effectiveness of the six commonly used attachment materials (cotton canvas, burlap, denim, polyester fiber, coated nylon fabric, and gauze). The results revealed that the cotton canvas, polyester fiber, and coated nylon fabric performed best in terms of durability and adhesion. The cotton canvas was achieved in the highest biomass attachment of up to 5.19 g/(m²∙d). The poor attachment of the burlap, denim, and gauze was found with almost zero attached biomass, unsuitable for the attachment materials for the reactors. Subsequently, the three attachment materials (cotton canvas, polyester fiber, and coated nylon fabric) were applied to a revolving algal biofilm reactor. It was found that the cotton canvas achieved the highest biomass attachment, with an average biomass of 16.00 g/m², and a microalgae productivity of 1.60 g/(m²∙d). Structural characterization analysis showed that the complex surface of the cotton canvas was observed with a velvety texture of fibers, thus providing an excellent environment for the attachment and growth of the microalgae. Polyester fiber and coated nylon fabric followed, but in terms of the total biomass, the coated nylon fabric treatment group reached the highest at 13.94 g. The cotton canvas was less costly and easier to hang film than coated nylon, indicating a better economy. The pigment content of the microalgae was positively correlated with the biomass. There was a decrease in the incubation time. In suspended microalgae, the coated nylon fabric treatment was significantly higher than the cotton canvas and polyester fiber ones. A series of experiments was carried out on a rotating biofilm system in order to treat the simulated anaerobic digestate food waste effluent. The coated nylon fabric and cotton canvas shared relatively excellent pollutant removal. The removal rates of the total nitrogen, ammonia nitrogen, nitrate nitrogen, total phosphorus, and chemical oxygen demand by coated nylon fabric were 67.2%, 99.6%, 56.6%, 98.7%, and 95.8%, respectively. In the cotton canvas treatment, the removal efficiencies for the total nitrogen, ammonia nitrogen, nitrate nitrogen, total phosphorus, and chemical oxygen demand reached 50.6%, 99.5%, 28.5%, 98.7%, and 97.0%, respectively. In the polyester treatment, the removal efficiencies of the total nitrogen and nitrate nitrogen were only 35.8% and 15.9%, respectively. The extracellular polymeric substances (EPS) revealed that the content of EPS in the suspended and attached microalgae in the three-reactor treatment first increased and then decreased with the extension of cultivation time. The consumption of the EPS by attached microalgae was used to explain the peeling off of some parts of the biofilm at the end of the cultivation. Wall-adherent microalgae greatly contributed to the more EPS, in order to cope with the stress and protect themselves. The fluorescence intensity of the EEM corresponded to the content of EPS, where the main organic matter was dissolved in the microbial by-products. It was recommended that the cotton canvas be better selected as the material for the biofilm growth attachment. As such, the better performance was achieved in the attached biomass of the microalgae and pollutant removal efficiency. The finding can also provide a strong reference for the attached microalgae biofilm in wastewater purification.