Water-soluble　poly(ethylene　oxide)-block-poly　(propylnen　oxide)-block-poly(ethylene　oxide)　(PEO-PPO-PEO)　copolymers　are　nonionic　macromolecular　surface-active　agents,　available　commercially　as　Pluronics.　Recently,　the　micellization　of　these　copolymers　has　been　focused　because　of　a　strong　interest　in　Pluronic　micelles　as　drug-microcarriers　in　therapeutic　cream　and　ointments.　However,　micellization　of　Pluronic　copolymers　is　very　complex　compared　with　those　conventional　surfactants.　Due　to　this　reason,　interaction　of　binary　Pluronics　has　been　hardly　studied　up　to　now.　This　paper　reported　the　micellization　of　binary　Pluronic　molecules　P94/L92　and　F108/L92　which　have　similar　length　in　PPO　blocks　and　different　length　in　PEO　blocks,　as　well　as　P94/L64　which　have　different　length　in　PPO　blocks.　I-2　was　used　as　a　probe　to　determine　the　critical　micelle　concentration　(cmc)　of　the　mixtures　in　aqueous　solutions.　This　method　has　been　confirmed　to　be　very　sensitive　to　the　determination　of　cmc.　The　results　showed　that　P94/L92　or　F108/L92　binary　components　interact　each　other　to　form　mixed　micelles　over　the　range　of　all　concentration　ratio.　With　addition　of　L92　molecules　with　a　shorter　PEO　block,　hydration　of　P94/L92　or　F108/　L92　mixed　micelles　was　weakened　duo　to　a　decrease　in　the　number　of　EO　groups　within　the　shell.　When　the　mass　fraction　of　L64,　W-L64　＜　0.　4,　the　micellization　in　P94/L64　mixtures　was　hindered　and　the　cme　of　P94　was　enhanced　to　a　higher　value　due　to　the　formation　of　P94/L64　mixed　pre-micelles　in　aqueous　solution.　Theses　mixed　pre-micelles　have　weaker　hydrophobicity　compared　with　those　pre-micelles　formed　with　individual　P94　molecules.　Over　the　range　of　w(L64)　＜　0.　4,　therefore,　there　was　only　the　micelles　formed　with　individual　P94　molecules　when　the　micellization　took　place.　With　further　increasing　w(L64),　the　mixed　micelles　of　P94/L64　started　to　be　formed　and　the　critical　point　of　mixed　micelle　formation　was　determined　at　w(L64)　=　0.　4.