The processes of threshing and cleaning of desmodium seeds were preliminary studied, in order to evaluate its capability to increase the amount of pure live seed in the seed lot. The threshing system of frictions through discs complementary to the work done by the cylinder and concave of the harvesting combine, along with a processing sequence of air screen cleaner and gravity table were used. The results of purity and germination tests after the cleaning process indicated that: the complementary threshing system was efficient as far as threshing is concerned; it is also an excellent seed conditioner due to the escarification imposed to the seeds, which increased the percentage of normal seedling in 20%. The cleaning process of seeds done by the air screen cleaner and upgrading through the gravity table increased the amount of pure live seed from 14,4% of original seed lot to 74,2% of the processed seed.