Multi‐block copolymers consisting of poly(tetrahydrofuran) (PTHF) as the hydrophobic part and poly(ethylene oxide) (PEO) as the hydrophilic part were synthesized using lipase‐catalyzed polymerization. The self‐assembly micelle of the synthesized copolymer in the presence of water was investigated using fluorescence spectroscopy and dynamic light scattering. Fluorescence spectroscopy measurements suggested that the copolymers were associated in water to form polymeric micelles, and the critical micelle concentrations (CMC) value of the block copolymers was 0.0005–0.005 mg/ml.