The invention provides an isoprene rubber preparation method and a polymerization system thereof and a catalyst feed device. The method includes: a raw material preparation step in which an organic solvent and isoprene monomer are added in a plurality of polymerization reactors in series, and the polymerized isoprene monomer concentration is 8g-14g of monomer/100mL of the solvent; a processing parameter setting step in which the polymerization temperature and the polymerization pressure of the plurality of polymerization reactors are set; a catalyst addition step in which at least a catalyst and a solvent are added into the first polymerization reactor through the catalyst feed device; and an isoprene rubber generation step in which the isoprene monomer is polymerized in the first polymerization reactor and other polymerization reactors in the presence of the catalyst, and a reaction product isoprene rubber is obtained in the last polymerization reactor. The invention also discloses an isoprene rubber polymerization system of the isoprene rubber polymerization system and the catalyst feed device therefor.