Production process of olefin polymer

A process for producing an olefin polymer, comprising:

• step (I) preliminarily polymerizing an olefin at 65° C. or lower in the presence of a preliminary polymerization catalyst prepared by bringing the following components (A), (B) and (C) into contact with each other, to produce a preliminary polymerization catalyst component (X);
• and
• step (II) polymerizing an olefin in the presence of a polymerization catalyst prepared by bringing the preliminary polymerization catalyst component (X) into contact with the following components (D) and (E), to produce an olefin polymer;
• wherein component (A) is metallocene-based complex,
• component (B) is a solid co-catalyst component in which a compound capable of ionizing the metallocene-based complex into an ionic complex is supported on fine particle support, component (C) is an organoaluminum compound represented by the general formula R13Al, wherein R1 is a linear hydrocarbon group of 1 to 8 carbon atoms, and each R1 can be the same or different,
• component (D) is an organoaluminum compound represented by the general formula R23Al, wherein R2 is a branched hydrocarbon group of 3 to 8 carbon atoms, and each R2 can be the same or different, and component (E) is an electron donating compound,
• wherein component (B) is produced by bringing diethyl zinc (component (a)), fluorinated phenol (component (b)), water (component (c)), fine inorganic particulate carrier (component (d)) and alkyl disilazane (component (e)) into contact with each other, and
• wherein the molar ratio of Al atom of the organoaluminum compound as component (C) to be contacted in the step (I) to a transition metal of the metallocene-based complex (component (A)) is 0.05 or more and less than 5.