Objective: to evaluate nutritional supplement with soy milk for children under 5 years old in Yen Son district, Tuyen Quang during 6 months. Subjects and Methods: an interventional study was conducted in children under 5 years old at two communes in Yen Son district, Tuyen Quang. Results: rate of malnutrition (W/H) was 34.4 percent level I, level II was 8.4 percent, 0.7 percent grade III/, W/A level I was 36 percent. 7.4 percent grade II, grade III was 1.2 percent. H/A was 5.3 percent level I, level II was 3.2 percent, grade III was 1.2 percent. Supplement soy milk for children under 5 years old index W/H index and W/A and have distinctly different with statistical significance p 0.05. Indicators height/age difference is not significant. Conclusion: The soy milk supplement can reduce the incidence of underweight malnutrition in children under 5 years old.