Abstract: Abstract: In order to evaluate the effect of organic fertilizer based on aquatic plant composting on the rice yield and paddy soil properties, a four-year field experiment was carried out in the typical paddy field of the Tai Lake region. The four-year field experiment was composed of different combinations of organic nitrogen substitute of aquatic plant compost and mineral urea, and it included 6 treatments whose proportions of organic nitrogen were 0, 20%, 40%, 60%, 80% and 100% of total nitrogen amount, respectively; and for all the treatments, the total nitrogen inputs were the same. Grain yield, yield components, the uptake of nitrogen, phosphorus and potassium in rice straw and grain as well as the concentration of soil organic carbon and soil total nitrogen and pH value in the top soil layer were measured. Our study revealed the following findings: Firstly, compared to mineral urea alone, combined application of both organic fertilizer of aquatic plant composting and mineral urea had a good potential to improve the grain yield of rice, and with the increase of organic fertilizer ratio, rice yield tended to increase first and then afterwards decrease. When the replacement of organic fertilizer was 40% and 60% of total nitrogen, the rice yield reached the highest point. Applying organic fertilizer alone had similar grain yield of rice as the treatment of applying urea alone. Secondly, the number of productive tillers was significantly reduced with sole organic fertilizer, while the phenomenon could be diminished or eliminated by combined application of compost and mineral urea. The parameters including the number of productive tillers, spikelets per panicle and percentage of filled grains were all relatively higher when the organic nitrogen substitutes were at the ratio of 40% and 60% of total nitrogen input. Thirdly, with the increase of organic fertilizer application, the nitrogen concentration in straw was decreased, while no pronounced effect was found for the nitrogen concentration in grain. Furthermore, no significant difference was found for the phosphorus uptake in grain or straw among all the treatments. The potassium uptake of straw was significantly improved with the addition of organic fertilizer, and meanwhile the potassium uptake of grain was significantly enhanced when the substitute rate of organic fertilizer was 80% of total nitrogen. Lastly, there was positively significant correlation between the soil total nitrogen, soil organic carbon and pH value, and the amount of organic fertilizer application. With the addition of organic fertilizer, the soil total nitrogen and soil organic carbon were significantly increased compared to that of 4 years ago. When the organic nitrogen was applied at 80% and 100% of total nitrogen, the soil pH value was also significantly higher than that of 4 years ago. In conclusion, the combined use of aquatic plant compost plus with mineral urea is beneficial to improve the grain yield of rice, enhance soil organic matter as well as decrease the soil acidification, which is a protective and environmental-friendly fertilization technology in Tai Lake region.