The present invention provides a raw material for forming a strontium-containing thin film of a cyclopentadienyl-based strontium compound, which is in the liquid state at room temperature to 50.degree. C., can be purified by distillation, present as a monomer, has high vapor pressure, and suitable for mass production, and a process for preparing the same. Sr[C.sub.5(CH.sub.3).sub.4(C.sub.3H.sub.7)].sub.2 is prepared by reacting Na[C.sub.5(CH.sub.3).sub.4(C.sub.3H.sub.7)].sub.2 or K[C.sub.5(CH.sub.3).sub.4(C.sub.3H.sub.7)].sub.2 with SrI.sub.2 in THF to produce a THF adduct of Sr[C.sub.5(CH.sub.3).sub.4(C.sub.3H.sub.7)].sub.2; evaporating THF and extracting the residue with toluene to give a toluene solution; evaporating toluene and drying the residue under reduced pressure; and heating to 100 to 160.degree. C. in vacuo to dissociate and remove THF and distilling.