The present invention provides a sustained release oral dosage form containing dalfampridine that can be administered once daily. The dosage form includes dalfampridine as the active pharmaceutical ingredient and the excipients comprising osmotic agents in a tablet core. The sustained release oral dosage form of the present invention can be administrated once daily and can provide a proper fluctuation index to reduce undesired adverse effect, prevent alcohol-induced dose dumping and release drug at a rate sufficient to maintain certain drug plasma concentration.