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A kind of trapezoidal slot-type pneumatic wheat seed-metering device was designed. Through experiments, the sucking seed uniformity of the seed-metering device with trapezoidal, U-shape, V-shape slot-type and the straight slot-type was analyzed. The experimental data showed the variation coefficient of the seed metering device with trapezoidal slot-type was the smallest, which was 7.0%, and the seed breakage rate was lower than 0.30%. These data conformed to the requirement of wheat precise seeding. But in the actual operation because of undulation of negative pressure of the wind machine and difference of air current suction in each row slot-type, the consistency of each line seeding quantity of the seed-metering device was not improved. Its variation coefficient was not more than 4.4% in the different speed change situations. 