Pore-filling membranes filled with quaternized poly(styrene-co-ethylene glycol dimethacrylate) were prepared with the degree of crosslinking (DC) for reverse electrodialysis (RED). It was shown in power density performance that the pore-filling membranes with low DC had lower open circuit voltage (V-oc) and resistance, but those with high DC had higher V-oc and resistance than the commercial AMX membrane. Thus, the compromise between their transport number and resistance is necessary for the application of pore-filling membranes in RED.