Guaifenesin is an expectorant and belongs to BCS class I which exhibits high solubility and high permeability. Guaifenesin has a half-life of 1 hour; in order to increase its duration of action gastroretentive tablets are formulated. Guaifenesin shows poor flow properties so the method opted for the preparation of this tablets is Top spray granulation. In which HPMC K100LV/HPMC E6LV/HPMC K100M/HPMC K15MPCR is used as swelling matrix polymer, Povidone is used as binder, Magnesium stearate is used as lubricant and MCC is used as diluent. Tablets are evaluated for floating lag time, total floating time, thickness, hardness, friability and invitro drug release studies were performed. The optimized formulation showed less floating lag time, sufficient floating time and with maximum drug release of 88.9% at the end of 12 hours.