The invention relates to a norbornene, octafluorocyclopentene and acrylonitrile ternary polymerization catalyst and a ternary polymerization method. The preparation method of the catalyst is characterized by comprising the following steps that rhodium acetate, butyl lithium and a ligand are dissolved into a first solvent in a three-mouth flask in a dry inert atmosphere, constant-temperature stirring is conducted for 20 min to 50 min at the speed of 130 rpm to 170 rpm at the temperature of 20 DEG C to 50 DEG C, and then a rhodium-lithium complex catalyst is obtained; norbornene, octafluorocyclopentene and acrylonitrile monomers are taken according to the molar ratio of 1:1:1, added into a high-pressure kettle which is vacuumized and subjected to nitrogen filling for many times and dissolved by adding a second solvent; the rhodium-lithium complex catalyst is added, and reacting is conducted for 1 hour to 6 hours at the temperature of 50 DEG C to 150 DEG C under the pressure of 0.1 MPa to 10 MPa; a product obtained through reacting is poured into an ethanol solution containing 4 wt%-5 wt% of hydrochloric acid, an obtained precipitate is washed with ethanol until the precipitate is neutral, vacuum drying is conducted, and then the norbornene, octafluorocyclopentene and acrylonitrile terpolymer is obtained.