Use of an iron bipyridine complex in the polymerization of conjugated dienes, wherein the method for polymerizing conjugated dienes comprises the following method: under an inert gas atmosphere a solvent and a conjugated diene monomer are sequentially added into a reactor and stirred, then added with a catalyst system premix, polymerized at a constant temperature of -40°C-50°C for 10 min-720 min, added with a quencher and an antiaging agent after the reaction is finished, washed with ethanol, and separated and purified to obtain a poly(conjugated diene) product; wherein the catalyst system premix is prepared from the iron bipyridine complex and a cocatalyst or prepared from the iron bipyridine complex, a cocatalyst and a dealkylation reagent; the iron bipyridine complex having a structural formula of any one of the following formulas: wherein R 1 , R 2 , R 3 and R 4 are the same or different; R 1 , R 2 , R 3 and R 4 respectively represent any one of H, CH3, phenyl, methoxy or nitro; where the catalyst system premix is prepared from the iron bipyridine complex and the cocatalyst, the molar ratio of the cocatalyst to the iron bipyridine complex is (5-1000) : 1; the molar ratio of the conjugated diene monomer to the iron bipyridine complex is (10000-25000) : 1; and the volume ratio of the conjugated diene monomer to the solvent is 1:(2-50); where the catalyst system premix is prepared from the iron bipyridine complex, the cocatalyst and the dealkylation reagent, the molar ratio of the cocatalyst to the iron bipyridine complex is (5-200):1; the molar ratio of the conjugated diene monomer to the iron bipyridine complex is (1250-10000) : 1; the volume ratio of the conjugated diene monomer to the solvent is 1:(2-50); and the molar ratio of the dealkylation reagent to the iron bipyridine complex is (1-10):1. under an inert gas atmosphere a solvent and a conjugated diene monomer are sequentially added into a reactor and stirred, then added with a catalyst system premix, polymerized at a constant temperature of -40°C-50°C for 10 min-720 min, added with a quencher and an antiaging agent after the reaction is finished, washed with ethanol, and separated and purified to obtain a poly(conjugated diene) product; wherein the catalyst system premix is prepared from the iron bipyridine complex and a cocatalyst or prepared from the iron bipyridine complex, a cocatalyst and a dealkylation reagent; the iron bipyridine complex having a structural formula of any one of the following formulas: wherein R 1 , R 2 , R 3 and R 4 are the same or different; R 1 , R 2 , R 3 and R 4 respectively represent any one of H, CH3, phenyl, methoxy or nitro; where the catalyst system premix is prepared from the iron bipyridine complex and the cocatalyst, the molar ratio of the cocatalyst to the iron bipyridine complex is (5-1000) : 1; the molar ratio of the conjugated diene monomer to the iron bipyridine complex is (10000-25000) : 1; and the volume ratio of the conjugated diene monomer to the solvent is 1:(2-50); where the catalyst system premix is prepared from the iron bipyridine complex, the cocatalyst and the dealkylation reagent, the molar ratio of the cocatalyst to the iron bipyridine complex is (5-200):1; the molar ratio of the conjugated diene monomer to the iron bipyridine complex is (1250-10000) : 1; the volume ratio of the conjugated diene monomer to the solvent is 1:(2-50); and the molar ratio of the dealkylation reagent to the iron bipyridine complex is (1-10):1. <EOS>