Abstract: Breeding test fields require the sowing of thousands of plots. Different varieties need to be sown in each plot, and the seeds cannot be mixed between plots. The plot seeder has requirements such as continuous sowing and interval sowing. Therefore, the seeder needs to be frequently cleaned and replaced seeds, which is also the biggest difference from the field seeder. Neatly-arranged aisles can strengthen the isolation between varieties and reduce mutual influence. At the same time, it is convenient for researchers to walk in the aisle between plots to conduct field surveys and for plot harvesters to distinguish different plots during harvesting. However, the existing maize plot planters inevitably have the phenomenon that maize seeds are sown on the aisle between plots. There are two main reasons for excessive seeding in the seed metering device. First, the seeds in the seed filling cavity are not cleaned in time, resulting in the seed plate absorbing excess seeds. Second, the seed plate is filled with seeds too early at the moment when the seeds of the next plot enter the seed filling cavity. Air-suction seed metering devices are used by most plot precision seeders due to their better seeding performance. Aiming at the problem of poor consistency of aisle width between maize plots, the study put forward the technical idea of accurately blocking the excess seeds adsorbed by the seed plate to enter the seed throwing area, designed a blocking type air-suction seed metering device. This study added a blocking function to the traditional plot seed metering device's filling-cleaning-changing functions to achieve continuous filling-blocking-cleaning-changing automated operations of the plot seed metering device. The movement trajectory of the blocked seeds were reasonably planned. Mechanical and kinematic analyses were conducted on maize seeds in the seed blocking stage. Based on the brachistochrone curve principle, the key parameters of the blocking mechanism were determined. brachistochrone curved surface was used as the contact surface between the blocking plate and the blocked seed. And the main parameters of the rotating circle corresponding to the brachistochrone curved surface were determined as a radius of 53.70 mm and a rotation angle of 0.482π. The function of the linkage plate in the blocking mechanism is to prevent the seed cleaning airflow from sucking away the seeds to be sown on the seed plate during seed cleaning, causing missed sowing. And the key parameters of the blocking mechanism were determined. A two-factor six-level full factorial bench test was carried out using the reaction distance of blocking plate triggering the closing action and the closing state duration distance as the test factors. The results showed that the probability of adsorbing one more seed at the end of the previous plot was 33.33%, and the probability of adsorbing one more seed in advance of the next plot was 10.00%. The reaction distance after the blocking plate triggering the closing action and the closing state duration distance had significant influence on the blocking effect. When the reaction distance was 1.2 m and the duration distance was 0.8 m, it can successfully block 4 suction holes between the neighbouring plots of the seed discharging plate, and it does not affect the normal seeds to be sown. The optimal operation parameters were verified through field tests. The results showed that the blocking success rate of the blocking type air-suction seed metering device was 100%, and the coefficient of variation of aisle width between plots was 4.19%. The coefficient of variation had decreased by 9.47% compared to the traditional air-suction seed metering device. Indicating that the alignment of aisle between plots in the maize plot after operation using the blocking type air-suction seed metering device was better. The blocking mechanism met the actual operational requirements. The study can provide technical reference for the further improvement of maize plot seeder.