The synthesis of tetra-armed star shaped poly(tetrahydrofuran)(THF) has been attempted using pentaerythritol tetrakis(3,4-epoxybutanoate(PETE) as a precursor by photoinduced cationic polymerization. The cationic polymerization of THF was initiated by photoirradiation with 500w high pressure mercury lamp, using PETE as a precursor, in the presence of diphenylidonium hexafluorophosphate(initiator) and followed by dark reaction. The polymerization behaviors, i.e., oyo conversion to polymer, the number of arms and gel formation have been discussed in relation to reaction parameters such as concentrations of PETE, salt and THF. The number of arms in star shaped polymers were determined by dividing the molecluar weight of polymer before alkaline hydrolysis by those of after alkaline hydrolysis. The number of arms of star shaped polymers were found to be strongly dependent on the molar ratio of THF/PETE and varied in the range of 2.5-11.2. It was observed that tetra-armed star shaped polymers was obtainable in the early stage of dark reaction from the systems where the molar ratio of THF/PETE in the feed was kept at around 1000.