The invention relates to a chemically-bonded HEDP (1-hydroxy ethylidene-1, 1-diphosphonic acid) medium-temperature organic polysiloxane phosphate based proton exchange membrane. The membrane is prepared by the following steps: firstly, under protection of nitrogen, mixing dimethyl sulfoxide and HEDP, stirring to obtain clear and transparent mixture, and performing reflux reaction at 160 DEG C; removing the dimethyl sulfoxide after the solution is cooled to 110 DEG C to obtain 1,1-vinyl diphosphonic acid liquid; secondly, mixing 1, 1-vinyl diphosphonic acid, 3-(methacryloxy) propyl trimethoxyl silane, 2, 2'-azobisisobutyronitrile and ethanol, stirring at 60-80 DEG C to react, cooling to room temperature, adding diluted hydrochloric acid, and stirring to obtain clear and transparent sol; thirdly, performing gelation to the sol to obtain a gel membrane; and fourthly, drying the gel membrane to obtain the chemically-bonded HEDP medium-temperature organic polysiloxane phosphate based proton exchange membrane. The membrane has high proton conductivity under medium temperature and low humidity and has excellent flexibility and mechanical property.