Vanadium complexes with unsymmetric bulky ligands 2-[1-(2,6-dibenzhydryl-4-methylphenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridine (V1-V3) and symmetrical bulky ligand 2,6-bis(1-(2,6-dibenzhydryl-4-methylphenylimino)ethyl)pyridine (V4) were prepared and thoroughly characterized. Single crystals of V1 and V4 were further tested with X-ray single crystal diffraction to prove the molecular structures, and a distorted triangular biconical geometry was adopted around vanadium centers of V1 and V4. These vanadium complexes bearing bulky ligands displayed moderate to high catalytic activity (up to 24.0 × 106 g molV-1 h−1) toward ethylene polymerization when ethylaluminum sesquichloride was employed as a cocatalyst, affording moderate to ultrahigh molecular weight polyethylenes (18.7 × 104 to 176.9 × 104 g/mol). Compared with the classical bis(imino)pyridine vanadium complex VR, complex V3 demonstrated a long lifetime as well as excellent thermal stability. Furthermore, polyethylenes derived from complexes V1-V4 had significantly higher molecular weights at high temperatures.