A method for preparing nickel catalysed cis -polybutadiene and rare earth catalysed cis -polybutadiene, characterized by comprising: S 1, providing a set of polymerization equipment comprising a polymerization unit and an agglomeration unit; S2, preparing a nickel catalysed cis -polybutadiene by following steps: S21, adding butyl oil, nickel-based catalyst into the polymerization unit to obtain a nickel catalysed cis -polybutadiene liquid; S22, adding the nickel catalysed cis -polybutadiene liquid into the agglomeration unit to agglomerate, and obtaining the nickel catalysed cis -polybutadiene; and S3, preparing a rare earth catalysed cis -polybutadiene by following steps: S31, adding butyl oil, rare earth-based catalyst into the polymerization unit to obtain a rare earth catalysed cis -polybutadiene liquid; S32, adding the rare earth catalysed cis -polybutadiene liquid into the agglomeration unit to agglomerate, and obtaining the rare earth catalysed cis- polybutadiene, wherein in the step S2 and step S3, the butyl oil comprises a butadiene monomer and a solvent, a mass ratio of an oxygen containing compound of the butyl oil to the butyl oil is less than or equal to 20 mg: 1 kg, and a mass ratio of water of the butyl oil to the butyl oil is less than or equal to 50 mg: 1 kg, and step S2 and step S3 are interchangeable, and an interchange is performed without stopping and cleaning the polymerization equipment, i.e., the polymerization is continuous. S 1, providing a set of polymerization equipment comprising a polymerization unit and an agglomeration unit; S2, preparing a nickel catalysed cis -polybutadiene by following steps: S21, adding butyl oil, nickel-based catalyst into the polymerization unit to obtain a nickel catalysed cis -polybutadiene liquid; S22, adding the nickel catalysed cis -polybutadiene liquid into the agglomeration unit to agglomerate, and obtaining the nickel catalysed cis -polybutadiene; and S21, adding butyl oil, nickel-based catalyst into the polymerization unit to obtain a nickel catalysed cis -polybutadiene liquid; S22, adding the nickel catalysed cis -polybutadiene liquid into the agglomeration unit to agglomerate, and obtaining the nickel catalysed cis -polybutadiene; and S3, preparing a rare earth catalysed cis -polybutadiene by following steps: S31, adding butyl oil, rare earth-based catalyst into the polymerization unit to obtain a rare earth catalysed cis -polybutadiene liquid; S32, adding the rare earth catalysed cis -polybutadiene liquid into the agglomeration unit to agglomerate, and obtaining the rare earth catalysed cis- polybutadiene, S31, adding butyl oil, rare earth-based catalyst into the polymerization unit to obtain a rare earth catalysed cis -polybutadiene liquid; S32, adding the rare earth catalysed cis -polybutadiene liquid into the agglomeration unit to agglomerate, and obtaining the rare earth catalysed cis- polybutadiene, wherein in the step S2 and step S3, the butyl oil comprises a butadiene monomer and a solvent, a mass ratio of an oxygen containing compound of the butyl oil to the butyl oil is less than or equal to 20 mg: 1 kg, and a mass ratio of water of the butyl oil to the butyl oil is less than or equal to 50 mg: 1 kg, and step S2 and step S3 are interchangeable, and an interchange is performed without stopping and cleaning the polymerization equipment, i.e., the polymerization is continuous.