The experiment included plant densities ranged from 8333-16667 plants/ha. The result showed that: Both varieties KM414 and HL28 in treatment 4 (10.000 plants/ha) had the most stable and strongest growth. In treatment 4 (10.000 plants/ha), KM414 and HL28 varieties reached the highest fresh tuber yield (44.77 tons/ha and 40.77 tons/ha), highest quality and net interest (46.44 52.44 million/ha) , which higher than the control and other treatments. KM414 had higher yield, quality and economic efficiency than HL28. It could be planted the KM414 and HL2004-28 at plant density of 10.000 plants/ha (1.0 x 1.0 m spacing) in Thai Nguyen province as well as other cassava cultivation areas in the Northern mountainous region of Vietnam to get high yield and economic effeciency.