Abstract: The present invention relates to a novel ligand derived from a tetrahydroquinoline derivative, and a transition metal compound prepared using the ligand, where an amido ligand is linked to an ortho-phenylene ligand to form a condensed ring and a 5-membered cyclic pi-ligand linked to the ortho-phenylene ligand is fused with a heterocyclic thiophene ligand. Compared with the catalysts not fused with a heterocyclic thiophene ligand, the transition metal compound of the present invention as activated with a co-catalyst has higher catalytic activity in olefin polymerization and provides a polymer with higher molecular weight.