In drug delivery system, diverse kinds of materials were developed through the researches. Among them, block copolymer micelles have been promising vesicles to carry hydrophobic molecules. Among many kinds of block copolymers, amphiphilic micelles consisting of PEG and PDLLA, are effective drug carriers due to its outstanding biocompatibility of the hydrophobic group. It degrades into acid in the cell. Another advantage is high aqueous solubility of hydrophobic drugs in hydrophobic cores surrounded by hydrophilic coronas. In this work, Forster resonance energy transfer (FRET) is applied to identify the release of hydrophobic drug molecules. As a model of drugs, FRET pairs, DiI as an acceptor and DiO as a donor, were encapsulated into self-assembled polymeric micelles in water as drug molecules are encapsulated in nanocarriers. To demonstrate the idea, we vary the ratios of hydrophilic and hydrophobic group so that the thickness of hydrophilic surface is adjusted. Depending on the different FRET efficiency of each type of micelles, cargo release through micelle-micelle collision will be investigated. Through this work, we demonstrate how drug molecules are released from polymeric micelle system.