Objective: To assess activity of prevention malnutrition in children under 5 years old Bach Thong district, Bac Kan in 2011. Subjects and Methods: retrospective study was conducted on networl of prevention of malnourished children (health workers, government leaders, unions...), the pregnant women and mothers with children under 5 years. Results: The rate of malnutrition in children was 20.6 percent. Network of prevention of malnourished children was built from districts to villages in Bach Thong. Equipment and health workers for the program was relatively complete from district to village. Collaborators of prevention of malnourished program have participated training courses. Activities of program: weight infants reached 95.7 percent, taking vitamin A for child 6 to 60 months was 96.3 percent, de-worming for children 24 to 60 months was 95.2 percent and full immunization for children under 1 year to reach 95.6 percent. Conclusion: The rate of malnutrition of children under 5 years old in Bach Thong lower than the overall incidence of Bac Kan province. Prevention activities among children in Bach Thong SOD is relatively good.