Abstract: In view of the frequent occurrence of harmful algal blooms in rivers, lakes and reservoirs, high-efficiency flocculants and natural clay minerals are commonly used to remove algae, but there are some problems, such as large amounts of clay minerals, silt and thickening of sediments. The sunken algae will still wait for an opportunity to erupt and other shortcomings, unable to achieve a satisfactory algae removal effect. In this paper, a lightweight floating mineral pumice was used as a carrier to prepare a chitosan-pumice floating composite algae-removing material that does not produce sediment. With microcrystal aeruginosa as the test object, the material ratio, dosage, the effect of pH and reaction time of the algae suspension on its flocculation and algae removal performance, the surface morphology and composition of the composite algae removal material were characterized by SEM and XRF, and the algae removal mechanism of the material was discussed by Zeta potential measurement. The results show that the optimal preparation and use conditions are: chitosan-pumice ratio is 10∶1, the pH of the algae suspension is 7, 100 mL of the algae suspension is added 6 g of the composite algae-removing material, and the reaction time is 180 minutes, the maximum removal rate of the composite material for turbidity (NTU) is 94%, and the removal rate for Chlorophyll a (Chl-a) can reach 98%; the reason for its excellent performance is that the surface of the material is uneven, large surface area, and its Zeta potential is positive. It is easy to adsorb and flocculate and neutralize the charge with negatively charged algae, causing the algae cells to continuously aggregate to form large flocs, showing a good floating algae removal effect.