A　pH　sensitive　polymer　was　prepared　by　copolymerization　of　methacrylic　acid　as　monomer,　diethylene　glycol　dimethacrylate　as,　cross　-linking　reagent,　heptane　as　porogen,　and　fluorescent　dye　eosin　as　indicator.　The　factors　of　influence　on　the　preparation,　and　the　character　of　the　pH　sensitive　polymer　for　pH　were　studied.　The　maximal　emission　wavelength　of　eosin　was　red　shifted　in　the　polymer　than　in　solution,　the　apparent　Ka　largened,　and　the　dissociation　equilibrium　of　indicator　was　shifted　to　acidity　direction,　because　the　polarity　of　polymer　diminished.　Under　the　optimal　condition,　the　calibration　curve　of　the　pH　sensitive　polymer　covered　the　range　of　pH　0-3.0　with　good　reproduction　and　reversibility.