Microalgae rich in enzymatic proteins and trace minerals are an increasingly favorable feed additive. Nevertheless, the harvesting and drying expenditures account for 20%-30% of the total microalgae production costs, restricting microalgae's extensive application. Unprocessed microalgae could directly participate in straw ammonification feed production by filtering microalgae solution using straw and then ammoniating the filter residues containing straw and microalgae. The microalgal biomass and turbidity removals decreased with the increase in microalgae solution volume during filtration. In contrast, they increased and gradually stabilized with the rise in corn straw height and bulk density but first increased and then decreased with the enlarging of corn straw particle size. The predominant microorganisms shifted from Actinobacteriota and Proteobacteria to the Firmicutes that can hydrolyze corn straw, containing Carnobacterium, Bacillus, and Sporosarcina, as well as Cyanobacteria generating potential Microcystin disappeared after filtration. The maximal biomass and turbidity removals after filtration reached 82.54% and 78.38% under the microalgae solution volume of 520 mL and the corn straw height, bulk density, and particle size of 45 cm, 0.20 g/cm