The invention discloses a rare earth butadiene rubber preparation method. The method comprises the following steps: under the existence of an organic solvent and a solution polymerization reaction condition, butadiene contacts a rare earth catalyst. The method is characterized in that the rare earth catalyst comprises a rare earth complex with a structure represented by a formula (I), wherein R1, R2 and R3 are respectively independently hydrogen or C1-C20 hydrocarbyl; R4 and R5 are respectively independently hydrogen or C1-C6 hydrocarbyl; Ln is one of rare earth metals; and THF is tetrahydrofuran. With the preparation method provided by the invention, the cis-1,4 structure content of the obtained rare earth butadiene rubber is high, and substrate conversion rate is high.