The present invention relates to a catalyst system for olefin oligomerization and a method for olefin oligomerization, and more specifically, a catalyst system for olefin oligomerization and a method for olefin oligomerization that have more improved supporting efficiency due to a ligand compound capable of functioning as a tether to a support, and thus, exhibit high activity in the olefin oligomerization even with smaller amounts of catalyst composition and cocatalyst, thus enabling more efficient preparation of alpha-olefins.