Aiming at the problems such as light weight, irregular shape and small particle size of tomato seeds, and difficult to realize precision seed metering, a pneumatic roller type seed-metering device was designed, which is mainly composed of positive pressure seed blowing device, convex drum, seed box, and vibration exciter. The adsorption force generated by the negative pressure in the drum absorbs the tomato seeds in the seed box and rotates together with the drum. The adsorption force generated by the negative pressure in the drum of the seed-metering device, enables the tomato seeds to rotate with the drum. When the adsorbed tomato seeds rotate with the drum to the seed feeding position, the seed metering is completed under the action of positive air blowing. The structural parameters of the drum were determined as the diameter of 142 mm, the length of 345 mm, the number of seed suction holes of 10 × 20, the hole spacing of 33.3 mm, and the hole diameter of 1.2 mm. The central composite designed experiment was carried out with the seed suction negative pressure, the drum rotation speed and the vibration frequency as experiment factors and the single grain rate, the replay rate and the missed seeding rate as performance evaluation indicators. The regression model was established to obtain the optimal working parameters of seed-metering device by multi-objective optimization method, which included the seed suction negative pressure of 530 Pa, the drum speed of 5 r/min, and the vibration frequency of 68 Hz. At this time, the missed seed rate of the seed-metering device is 3.7%, the replay rate is 3.2%, and the single seed rate is 93.1%.