Introduction : The use of Simvastatin antidiabetic drugs with herbs occurs a lot in the community. Mahanimbine which is one of the compounds in Kemuning leaves is known to have antihyperlipidemic effects. This study aims to determine the interaction through molecular docking of Simvastatin and Mahanimbine on Kemuning leaves extract against CYP3A4 as antidiabetic. Method : Protein structure was downloaded in RSCB and NCBI sites, Molecular docking methods are carried out using Vina Autodock software and interaction visualization using Discovery Studio Visualizer. Results : The results was showed that the value of Simvastatin complex free energy with CYP3A4 is -3.4 kcal/mol and an increase in stability after tethering with Mahanimbine is -3.9 kcal/mol. The Simvastatin and Mahanimbine complex have 29 Pi Alkyl hydrophobic bonds, 4 Hydrocarbon hydrogen bonds. Conclusion : The conclusion of this study is that Mahanimbine could improve Simvastatin stability and increased Simvastatin concentration in plasma.