In the present study, the activities of components and formation enthalpies of binary Si-Al and Si-B solutions are calculated by a molecular interaction volume model (MIVM). Contributing to investigating deeply the removal of impurities B and Al from silicon solutions, the Wagner self-interaction parameters of B, Al in dilute silicon solutions at 1693-1873 K were tried by the use of the MIVM. The predicted activities and formation enthalpies were compared to the reported experiment data from the literature, which show that thermodynamics properties of binary silicon solutions can be accurately predicted and this model can provide effective verification and forecast for experiment.