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: 1; the molar ratio of the conjugated diene monomer to the iron bipyridine complex is: 1; and the volume ratio of the conjugated diene monomer to the solvent is 1:; 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:1; the molar ratio of the conjugated diene monomer to the iron bipyridine complex is: 1; the volume ratio of the conjugated diene monomer to the solvent is 1:; and the molar ratio of the dealkylation reagent to the iron bipyridine complex is: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: 1; the molar ratio of the conjugated diene monomer to the iron bipyridine complex is: 1; and the volume ratio of the conjugated diene monomer to the solvent is 1:; 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:1; the molar ratio of the conjugated diene monomer to the iron bipyridine complex is: 1; the volume ratio of the conjugated diene monomer to the solvent is 1:; and the molar ratio of the dealkylation reagent to the iron bipyridine complex is:1.