The traditional PVA–boric acid method was modified using calcium carbonate as a pore-forming agent to form the macroporous structure and formulated macroporous carrier (MPC) post-crosslinked with glutaraldehyde. The pore volumes, pore structure, porosity, and swelling behavior of MPCs were evaluated. The crosslinking density of MPCs with four different crosslinker dosages was calculated from their swelling properties using the modified Flory equation. MPCs demonstrated high swelling capacity, large specific surface area, high diffusion coefficient, as well as chemical and mechanical strength. The high crosslinking degree MPCs resulted in high biomass densities and low activity yield and vice versa. The characterizations of MPC suggest significant potential of its use for microbial immobilization and provide a scientific basis for immobilized carrier design and optimization.