Four kinds of long-chain α-olefins, including hexene, octene, terpene, and decadiene, were selected as the monomers in the homopolymerization catalyzed by TiCl4/Al(i-Bu)3 to prepare ultra high relative molecular weight polyolefin drag reducing agent. The effects of polymerization conditions on the relative molecular weights of the polymers were investigated. The effect of the side chain length of the monomers on the crystallinity and drag reduction performance of the polymer were also discussed in detail. In order to obtain a relative molecular weight of higher than 3.50×106, the optimum polymerization conditions were determined as that the content of TiCl4 in the main catalyst was 5.2×10-4 mol/L, the volume ratio of monomer to solvent is 1:1, and the reaction time was at least 1440 mins. The 13C NMR results indicated that the polymerization was completed, and the resultant homopolymers were designated products. DSC and XRD measurements showed that as the side chain length of the polyolefin was increased, the crystallization was enhanced. The rotating disk system was used to test the polymer drag reduction rate. The results showed that the drag reduction rate tended to increase with the increase of the side chain length of the drag reduction agent when their relative molecular weights were the same.