Background: SAM is defined by WHO weight for height or length < –3 SD or bilateral pitting oedema or MUAC < 11.5 cm for children age group between 6 to 59 months. Aims and Objections: To observe the effect of oral magnesium therapy in children with severe acute malnutrition (SAM) on serum magnesium level. Material and Methods: This study was conducted from 2020 in Department of Pediatrics, Kamla Raja Hospital, G.R.M.C., Gwalior. Study design: Cross sectional observational study Sample size: 117. Study population: 6 to 59 months. Duration of study: 2 years. Statistical analysis: SPSS version 25. Methods: Weight, height and MUAC were measure at the time of admission and after 14 days of oral magnesium therapy. Observation and Results: Children comprises of 117. Out of these 40 (34.2%) children were from 6 months to 12 months, 36 (30.8%) were in age group 13 to 29 months41 (35.04%) from age group 25 to 60 months. Out of 117, 61 (52.1%) were male and 56 (47.9%) were female. Mean weight were 7.02±1.85 kg on admission and increased to 7.44±1.95 kg after 14 days of oral magnesium therapy. Mean height were remained the same. The MUAC was 11.17±0.72 on admission and increased to 11.41 cm after oral therapy. Conclusion: Children were low MUAC, loss of subcutaneous fat, lethargy mental status have higher chances of magnesia while age, gender and edema, skin changes have no relation with serum magnesium.