Abstract: Abstract: Auxiliary pollination is the most critical process during hybrid rice seed production. The uniform and sufficient pollination has significant meaning for improving seed setting rate and operating efficiency. In the process of pneumatic auxiliary pollination for hybrid rice seed production, the pollens move with airflow, the airflow fields of multiple parallel nozzles of jet pipe overlay, and the jet cone angle and nozzle air pressure are the most important characters in airflow field. Increasing jet cone angle can expand the coverage of airflow field and reduce blind area of pollination effect, and eventually improve the uniformity of auxiliary pollination. Increasing nozzle air pressure can improve the airflow speed and increase airflow penetration, which significantly influences the uniformity and sufficiency of pollen distribution and determines the propagation distance of pollens. In order to study the relationships among jet cone angle, nozzle air pressure and pipe parameters, and find the ideal combination of pipe parameters for pneumatic auxiliary pollination, the paper firstly analyzed the superposition principle of the airflow field formed by parallel multiple nozzles, and obtained the formulae of jet cone angle and nozzle air pressure. Chromatic smoke was generated by the smoke grenade and sprayed through the nozzle, and pictures of airflow field were taken by camera. Jet pipe diameter, pipe thickness, nozzle diameter of pipe were selected as 3 factors, jet cone angle and nozzle air pressure were selected as 2 evaluation indices, and the three-factor and five-level of single factor and multi-factor orthogonal tests were done. In experiment, initial airflow velocity of nozzle and vertical distance between airflow junction point and center line of jet pipe were measured, and 5 photos and 5 measurements were taken for each test; the range analysis and matrix analysis were carried out, the influence laws of various factors on airflow field characteristics and their weights were obtained, as well as the relationships between airflow field characteristics and jet pipe parameters. Results showed that the influences of nozzle diameter on jet cone angle and nozzle air pressure were very obvious. As the nozzle diameter of pipe increased, the nozzle air pressure and jet cone angle increased accordingly. The influence order of the 3 factors from high to low was nozzle diameter, pipe diameter and pipe thickness. The optimal combination of the factors to jet pipe was the pipe diameter of 63 mm, the pipe thickness of 5 mm, and the nozzle diameter of 12 mm. At this time, the jet cone angle was 13.38°, and the nozzle air pressure was 31.6 Pa. The optimal factors were verified by test. Pollination effects were evaluated by the selected 3 evaluation indices on effective distribution area ratio, average distribution density, nonuniformity of pollen distribution. The confirmatory test showed that the pollen distribution was more uniform, the effective distribution area ratio of pollen was obviously improved, the nonuniformity of pollen distribution (variance) dropped to 1.33, the degree of uneven distribution was significantly reduced, and the distribution images of pollen showed unimodal normal distribution. The pipe parameters can satisfy the requirements of auxiliary pollination, which provides important reference to the design of jet pipe for pneumatic auxiliary pollination in hybrid rice seed production.