Hydrogel is prepared using triblock copolymer of poly(ethyleneoxide-propyleneoxide-ethyleneoxide) with different block contents. Each hydrogel showed different rheological and thermal behavior according to the conditions of gelation such as solution temperature, the content of block copolymer, and block ratio between ethylene oxide and propylene oxide. In this hydrogel system, poly(propyleneoxide) and poly(ethyleneoxide) acted as hydrophobic and hydrophilic domains, respectively. In aqueous solution, block copolymer acts as a surfactant, and then formed micelles due to the hydrophilic-lyophobic balance. These micelles aggregated and formed a lattice structure. In temperature sweeping using Rheometer, transition of aqueous block copolymer solution was developed from a liquid state through soft-gel state to hard-gel state as increasing temperature. Hydrogels with different block ratio of PPO and PEO represent different sol-gel and gel-sol transition point.