To develop osmotic granule with semi-permeable membranes, we prepared the semipermeable membranes with different pore forming agent by using solvent casting method. The membrane was consisted of cellulose acetate, Eudragit® RS, hydroxypropylcellulose (HPC), and triethylcitrate (TEC) in the presence of PEG200, PEG1, 000, or dibutylsebacate(DBS) as a pore forming agent. The produced membranes were white and elastic and exhibited soft property on touch. The release amount of pore forming agent from membrane with different pore forming agent was measured in water dissolution media and the order was PEG200 > PEG1, 000 > DBS. The formation of pore in membrane was observed by morphological SEM image after dissolution. The pore formation and porosity of membrane depended on water solubility of pore forming agent. We confirmed that pores in porous semi-permeable membrane could be controlled by the pore forming agent.