The metallocene compound according to the invention and the olefin polymerization catalyst containing the compound are intended to produce a catalyst capable of preparing an isotactic polymer with a high polymerization activity. The metallocene compound contains a substituted cyclopentadienyl group and a (substituted) fluorenyl group and has a structure wherein these groups are bridged by a hydrocarbon group or the like. The process for preparing a metallocene compound according to the invention is intended to selectively prepare a specific metallocene compound so as not to produce an isomer, and in this process an intermediate product is synthesized by a specific method. The process for preparing a polyolefin according to the invention is intended to prepare a polyolefin having excellent impact resistance and transparency, and this process comprises homopolymerizing an .alpha.-olefin of 3 to 8 carbon-atoms or copolymerizing an olefin of 3 to 8 carbon atoms and another .alpha.-olefin in the presence of an olefin polymerization catalyst containing the above-mentioned metallocene compound.