An olefin polymerization catalyst having a high polymerization activity at high temperatures and a process for olefin polymerization using the catalyst are disclosed. The olefin polymerization catalyst comprises a transition metal compound which is represented by the following formula (I) and in which the net charge parameter of the central metal is not more than 2.00: ##STR1##

wherein M is a transition metal atom of Group 4 to Group 5 of the periodic table, m is an integer of 1 to 5, Q is —N or —C(R²), A is —O—, —S—, —Se— or —N(R⁵)—, R¹ is an aliphatic hydrocarbon group or an alicyclic hydrocarbon group, R² to R⁵ are each a hydrogen atom, a hydrocarbon group, an oxygen-containing group or the like, n is a number satisfying a valence of M, and X is a hydrogen atom, a halogen atom, a hydrocarbon group or the like.