Abstract: In this study, cellulose acetate membrane (0.45 μm) and polycarbonate membrane (0.4 μm) were compared by measuring nutrients in filtrates and chlorophyll a on the filters to explore the differences.Undried cellulose acetate membrane and polycarbonate membrane were both suitable for nutrients measurement with consistent results:there were no significant differences in nitrite, ammonium, dissolved phosphate and dissolved silicate between cellulose acetate membrane and polycarbonate membrane.The difference between these two membranes in nitrate was less than 2%.Dried cellulose acetate membrane introduced more ammonium to seawater samples due to the slow filtration rate.Polycarbonate membrane was more suitable for the determination of chlorophyll a.The retention efficiency of cellulose acetate membrane tends to be lower since it cannot retain the pico-phytoplankton completely.