Abstract: With three foreign optimal duckweed species as a reference, comparative experiments were conducted in the field of protein production capacity and freeze resistance capability of five local duckweed species in the Yangtze River delta area in the process of nitrogen-phosphorus wastewater purification. The results showed that local duckweed species Spirodela oligorrhiza and three foreign optimal duckweed species had pretty high level of protein production capacity(g/m²) and protein content in duckweed plants (dry material). Two local duckweed species(Spirodela oligorrhiza, Lemna perpusilla) and two foreign optimal duckweed species (Lemna minor 8627, Spirodella punctata 7776) could survive under low temperature condition and demonstrated fairly strong freeze resistance capability.