This article introduces the choice of drive systems, transmission ratio, number of cog, cog area of the wheel in cassava cuttings, planting combined machines. Cutters are the main part of the cassava cuttings, planting combined machines. In the process of working, transmission parts and cog wheel will affect the cut off power and space between 2 cassava cuttings on rows. Through the study, the authors have achieved some results of theoretical calculations: the distance between 2 cassava cuttings with agronomic request is U = 60, 70, 80 cm and the corresponding transmission ratio between the wheels of the planting machine to the blades is: i1 = 1.7
i2 = 1.99
i3 = 2.27. The number of cog on the wheel: 10
cog size: 100 x 80 mm
cog area: 80 cm2. The process of testing to see machines work efficiently: cassava cuttings are cut 100 percent, cuttings length 23 + (-) 1, gap between two cuttings on rows 70 + (-) 3.