Modern agricultural technologies of onion cultivation should follow high requirements for their planting. The construction of the onion planter coulter determines the quality of planting. The authors designed the drill coulter for sowing onions, which qualitatively prepares the planting furrow by leveling and compacting the surface of the furrow bottom. The use of skid coulters allows to hold them on a single row, that, including protection against damage during leveling and compaction of the furrow bottom in a single row unit, reduces the metal consumption of the coulter and increases its compactness. When determining the parameters of the coulter, considering the condition of stability of its movement when planting onion row units, a theoretical substantiation of the traction resistance was carried out. When determining the parameters of the coulter, taking into account the conditions of stability of its movement when planting the onion-sowing, a theoretical justification of the traction resistance was performed, with the possibility of regulating the pressure force of the coulter on the soil with a row spacing of 0.20 m, for the range of the speed of the sowing 3.6 …5.4 km / h, the depth of the coulter 30…50 mm when planting the onion-sowing. The design of the coulter and its theoretical justification are proposed, which makes it possible to reduce the traction resistance, as a result of which the emission of exhaust gases into the atmosphere is reduced. As a result of the uniform distribution of nutrition over the area and the uniformity of onion shoots, weeds are decline, which reduces the use of herbicides, and therefore increases the environmental friendliness of the products produced.