PURPOSE: To narrow molecular weight distribution by polymerizing a specified monomer, a cycloolefin, and a noncyclic 1-olefin.

CONSTITUTION: A mixture of 0.1-100 wt.% monomer of formulas I-VI (R1-8 are H, 1-8C alkyl), 0-99.9 wt.% cycloolefin of formula VII (n is 2-10), and 0-99.9 wt.% noncyclic 1-olefin of formula VIII (R9-12 are R1) is polymerized in the presence of a catalyst comprising alminoxane of formula IX and/or formula X (R13 is 1-6C alkyl, phenyl benzyl; n is 0-50) and metallocene of formula XI [M1 is Ti, Zr, Hf, Nb, Ta; R14-15 are H, halogen, 1-10C alkyl, etc.; R16-17 are each a monocyclic or polycyclic hydrocarbon residue which can form a sandwich structure with central atom M1; R18 is formula XII-XIV, etc., {R19-21 are each H, halogen, 1-10C (fluoro)alkyl, etc.; M2 is Ge, Sn}] at 0.01-4 bar and -78-150°C, and the polymerization is stopped when Mw/Mn becomes below 2.