Abstract: Abstract: At present, there are problems such as low production efficiency and high labor intensity in the weeding technology of rice direct seeding field, which will delay the best time of spraying and affect the growth of direct seeding rice. A kind of weed control technology and corresponding device with synchronous seeding and spraying were proposed in order to solve the technical problems of weeding, which were supported by the rice mechanical hill-drop drilling technology. The device's adaptability on field production and the active ingredients of herbicide residues and the dynamic rule of herbicide degradation in soil and water were studied as well. This research was carried out in early season of 2014, and early season and late season of 2015 respectively. Three kinds of herbicides, Pendimethalin, Sofit (pretilachlor) and Zhibojing (pretilachlor), were applied in this study to support rice mechanical hill-drop drilling technology with synchronously spraying herbicide. The research results were as follows: Firstly, the degradation rate of active ingredients in soil and water was above 95% after 20-23 days. Secondly, compared with Pendimethalin, Sofit had a better adaptability and a smaller influence on rice germination, growth and yield. Compared with the control treatment of no spraying herbicide (CK1), synchronous spraying Sofit treatment increased the rice yield by 4.02%-10.79%, and spraying Sofit 3 days after seeding increased the rice yield by 7.65%. Compared with spraying Sofit 3 days after seeding, the rice yield change of synchronous spraying treatment was only from -3.38% to 2.91%. Lastly, there were more active ingredients of herbicide by using the approach with synchronous seeding and spraying than that with spraying 3 days after seeding. Herbicide residue time in the water was found to be longer than that in the soil, and Sofit had a higher content of active ingredients than Zhibojing in both soil and water. The research results can provide reference for synchronous spraying with precision rice hill-drop drilling technology and machine. The research results show that this technology can not only ensure the herbicide effectiveness and grass control effect, but also improve production efficiency and reduce labor intensity. Because the application of synchronous spraying technology has just started, the technology needs more studies. From agronomy aspect, it must study the adaptability of various herbicides, spraying concentration and spraying conditions. From machinery aspect, it must research and develop advanced synchronous spraying herbicide device, especially to improve the uniformity of spraying, the synchronization of spraying and the intelligence of control.