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Aiming to the problem of pneumatic loss caused by the complex structure, dense arrangement, variable crosssectional area, bending, narrow and long characteristics of air passage on the pinholetube wheat widewidth precision uniform seeding mechanism. The fluid domain was divided into four regions according to the type of pneumatic transformation: variablearea longnarrow cylindrical zone, air pipeline curved zone, air chamber confluent zone and negative pressure port and air chamber connection zone. By analyzing the regions in the fluid domain that can lead to the pneumatic loss one by one, the principle and types of the pneumatic loss in each region were clarified. It was concluded that the diameter of the transverse air pipeline, the angle of the air pipeline and the diameter of the negative pressure port may have significant impact on the pneumatic loss. The above three parameters were taken as test factors, and the mean airflow velocity of seed hole, the minimum airflow velocity of seed hole and the standard deviation of seed hole velocity were taken as test indexes. The Fluent software was used to conduct the orthogonal simulation test of three factors and three levels. The influence degree of each parameter on the index was obtained by range analysis and variance analysis, and the best combination of parameters was determined as follows: the diameter of transverse air pipeline was 8mm, the angle of air pipeline was 105°, and the diameter of negative pressure port was 36mm. Under these parameters, the average air velocity of seed hole was 86.4m/s, the minimum air velocity of seed hole was 75.16m/s, and the standard deviation of seed hole velocity was 7.35m/s. Under the optimal parameters mentioned above, pinholetube wheat widewidth precision uniform seeding mechanism was verified, and the test result was slightly smaller than simulation result, but the trend was consistent, which proved the reliability of the numerical analysis.