Abstract: Abstract: Rice is one of the main food crops for more than 50% of the world's population. Mechanized rice direct seeding was roughly divided into broadcast seeding, drilling and hill seeding. The broadcast seeding was not conducive to the field growth and management, where the seeding precision was low, the distribution of rice seeds was irregular in the field, and the uniformity of seedling emergence was not good. In the drill seeding, the field distribution was better regular than that in the broadcast seeding. Since about 50% of rice planting area in China is hybrid rice at present, the drill seeding cannot meet the requirements of hybrid rice seeding, particularly suitable for the conventional rice because of its large seeding rate. The hybrid rice has stronger tillering ability and higher yield, compared with the conventional rice. Furthermore, only 3-5 seeds/hill is needed to form high-yield structure, when the mechanized direct seeding was adopted. In this study, a double-cavity pneumatic precision direct seeder was designed for the hybrid rice, with the seeding rate of 3-5 seeds/hill as the goal, thereby to meet the requirement of hybrid rice direct seeding in the field. The seeder was mainly composed of a double-cavity pneumatic seed metering device, gasoline vortex pump, negative pressure pipeline, ditching equipment, and transmission system, where the seed metering device was introduced, and the transmission system was designed. The vacuum pump was also selected, where the gradient reducing pipeline was designed to provide the air flow of negative pressure, according to the negative pressure of seed metering device. Taking the hybrid rice Yongyou 4949 as experimental materials, a field test was carried out under the various negative pressure of sucking seed, and forward speed of seeder (i.e., the rotation speed of sucking seed plate). An attempt was made to explore the effects of sucking seed negative pressure and the forward speed on seeding precision of double-cavity pneumatic rice precision direct seeder. As such, a new type of pneumatic direct seeder was designed with a double cavity for rice precision seeding, according to the requirement of direct seeding of hybrid rice in the field. A field experiment was also carried out to obtain the best working parameters, after the design for the main working parts of the seeder. The results showed that the average seeding qualified rate (3-5 seeds/hill rate) of seeder was 91.04%, the probability of 0-2 seeds/hill was 2.23%, the probability more than 5 seeds/hill was 6.73%, the average number of seeding was 4.16, and the variation coefficient of seeding qualified was 1.24%, when the negative pressure of sucking seed was 3.2 kPa and the forward speed of seeder was low (0.2-0.4 m/s). Two factors can be contributed to the values of parameters in field tests lower than those in laboratory tests. The uneven mud surface can determine the field work of seeder, due to the complex environment of field seeding can be detrimental to the performance of seed sucking, particularly on the vibration of seeder. In the uneven distribution of negative pressure, there was a significant influence on the seeding precision of seeds metering devices, where the others would not be able to achieve the optimal negative pressure of seed sucking, when some of seed-metering devices reached. In the field test, the probability of 0 seed/hill was 0. Compared with the original seeder with the single cavity and single sucking plate, the pneumatic rice precision direct seeder with the double cavity can effectively improve the probability of 0 seed/hill. The seeding precision can meet the requirement of direct seeding of hybrid rice in the field. The finding can provide a sound reference for the precision direct seeding and equipment of hybrid rice.