Osmotic drug delivery system utilize osmotic pressure as a energy source and driving force for delivery of drugs, pH presence of food under physiological factors may affect drug release from conventional controlled release system (Matrices and reservoirs), where as drug release from osmotic system is independent of these factors to a large extent. The aim of the current study was to formulate elementary osmotic pump tablets of water soluble Tramadol HCl. Formulation were prepared based on wet granulation method, coated with cellulose acetate solution containing varying amount of Dibutylphthalate (DBP), and Polyethylene glycol 400 (PEG-400). Drug release from the osmotic drug delivery system was studied using USP Type I Paddle type apparatus. The excipients of physio-chemical property of the drug were determined by DSC (Differential scanning calorimetry). The optimized formulation was subjected to accelerated stability testing as per ICH guidelines. Optimization results indicated that to a certain extent drug release was less effected by the orifice size, concentration of coating solution and coating weight. DSC showed the excipients used in the formulation did not alter physicochemical properties of the drug. The results confirmed that the factors responsible for drug release were osmotic agents (core) and orifice size membrane.