Transparent polycrystalline doped Yttrium Aluminum Garnet (YAG) has drawn considerable attention, especially for high power laser applications, where its use is beneficial over the single crystal YAG counterpart. Many studies have experimentally demonstrated the effect of silica addition on the enhanced densification kinetics of polycrystalline YAG. Different explanations for the roll of Si during the sintering have been proposed. However, no accurate data on the Si solubility limit in YAG yet exists. In the present work, Si solubility limit in YAG at the sintering conditions was carefully measured, using wavelength dispersive spectroscopy (WDS) in scanning electron microscope. In this respect the roll of Si additive during the YAG sintering will be discussed.