Abstract: [Objective] In order to provide some references for optimum duck stocking density in Zizania latifolia-duck farming, [Method] The biological properties, yield and quality of Zizania latifolia in Zizania latifolia-duck farmings with different duck stocking density were studied, taking monoculture Zizania latifolia as the control. [Result] The results showed that Zizania latifolia-duck farming had no significant effect on Zizania latifolia plant height, while increased leaf number and dry weight significantly, and delayed Zizania latifolia senescence late crops. When duck stocking density increased from 375 to 450 per hectare, Zizania latifolia senescence late crops was been accelerated. The average yield of Zizania latifolia-duck farmings was 26.31% higher than that of monoculture Zizania latifolia. When duck stocking density increased from 375 to 450 per hectare, the yield did not increase anymore. Zizania latifolia-duck farming significantly increased tiller number, percentage of swelling culms, Zizania latifolia N harvest index, N uptake efficiency and soil organic matter, available PK content after harvest. There were significant positive correlations between soil organic matter content and protein, vitamin C, amino acid of Zizania latifolia. There were significant negative correlations between soil available PK and nitrate content of Zizania latifolia. About 4500 m3 eutrophic water from culture pond was used for irrigating one hectare of Zizania latifolia-duck farming, and it inputted N, P, K equaled the NPK content of 99.75 kg urea, 38.25 kg superphosphate and 83.55 kg potassium chlorid. The optimum duck stocking density was 375 ducks per hectare in Zizania latifolia-duck farming under this experiment condition with conventional planting density of 27795 Zizania latifolia per hectare.