OBJECTIVE： To prepare Diphenidol hydrochloride double-layer osmotic pump tablets， and study its in vitro release characteristics. METHODS： Double-layer compressing technique and film coating technology were conducted to prepare Diphenidol hydrochloride double-layer osmotic pump tablets. The in vitro releases of it， Difenidol hydrochloride tablets in market， self-made Difenidol hydrochloride single-layer osmotic pump tablets were compared. RESULTS： The formulation was as follow as diphenidol hydrochloride 75 mg， sodium chloride 10 mg， low-molecular-weight polyoxyethylene 15 mg and right amounts of 5％ PVP K30 ethanol solution. Booster layer was high-molecular-weight polyoxyethylene 60 mg， sodium chloride 20 mg， PVP K30 6 mg， right amounts of magnesium stearate. 12 h cumulative release （Q） of prepared double-layer osmotic pump tablets reached 80％， and the release was in line with zero-order kinetic equation. Q15 min of Difenidol hydrochloride tablets had reached 90％； Q12 h of Difenidol hydrochloride single-layer osmotic pump tablets was only 51.14％. CONCLUSIONS： The prepared Difenidol hydrochloride double-layer osmotic pump tablets have sustained release effect， with more complete drug release within 12 h than single-layer one.