A method for preparing an olefin polymerization catalyst, comprising: first mixing an organic compound of Formula 1, an organometallic compound of Formula 2 and an aluminoxane, and then adding thereto a reaction mixture of an organic transition metal compound of Formula 3 and the aluminoxane and mixing, wherein: [Formula 1] R 1 -H or R 1 -Q-R 1 In Formula 1, R 1 is a cyclic hydrocarbyl group of 5 to 30 carbon atoms having at least 2 conjugated double bonds, and can be unsubstituted or partially substituted with 1 to 6 substituents which are selected from the group consisting of an alkyl group of 1 to 20 carbon atoms, an alkenyl group of 3 to 20 carbon atoms, a cycloalkyl group of 3 to 20 carbon atoms, a haloalkyl group of 1 to 20 carbon atoms, an aryl group of 6 to 20 carbon atoms, an arylalkyl group of 6 to 20 carbon atoms, an arylsilyl group of 6 to 20 carbon atoms, an alkylaryl group of 6 to 20 carbon atoms, an alkoxy group of 1 to 20 carbon atoms, an alkylsiloxy group of 1 to 20 carbon atoms, an aryloxy group of 6 to 20 carbon atoms, a halogen atom, an amino group and the mixtures thereof; Q is a divalent group selected from the group consisting of (CR 5 2) b, (SiR 5 2) b, (GeR 5 2) b, NR 5 and PR 5 for bridging R 1 S, wherein the substituent R 5 is independently a hydrogen atom, an alkyl radical of 1 to 20 carbon atoms, a cycloalkyl radical of 3 to 20 carbon atoms, an alkenyl radical of 1 to 20 carbon atoms, an aryl radical of 6 to 20 carbon atoms, an alkylaryl radical of 7 to 20 carbon atoms or arylalkyl radical of 7 to 20 carbon atoms, b is an integer of 1 to 4, when Q is (CR 5 2) b, (SiR 5 2) b or (GeR 5 2) b, the two substituents R 5 that are bonded to carbon, silicon(Si), germanium(Ge) can be connected with each other to form a ring of 2 to 7 carbon atoms, [Formula 2] M 1 R 2 m R 3 n R 4 p R 6 q In Formula 2, M 1 is an element selected from the group consisting of elements of Group 1, 2, 12, 13 and 14 of the Periodic Table, R 2, R 3, R 4 and R 6 are independently a hydrocarbyl group of 1 to 24 carbon atoms, an amide group, an alkoxy group or a halogen atom, m, n, p and q are independently 0 or 1, and m+n+p+q is equal to the valence of M 1, [Formula 3] M 2 R 7 r X s In Formula 3, M 2 is titanium(Ti), zirconium(Zr) or hafnium(Hf), R 7 is same as defined for R 1, X is a halogen atom, r is an integer of 0 or 1, s is an integer of 3 or 4, and r+s is equal to the valence of metal M 2. In Formula 1, R 1 is a cyclic hydrocarbyl group of 5 to 30 carbon atoms having at least 2 conjugated double bonds, and can be unsubstituted or partially substituted with 1 to 6 substituents which are selected from the group consisting of an alkyl group of 1 to 20 carbon atoms, an alkenyl group of 3 to 20 carbon atoms, a cycloalkyl group of 3 to 20 carbon atoms, a haloalkyl group of 1 to 20 carbon atoms, an aryl group of 6 to 20 carbon atoms, an arylalkyl group of 6 to 20 carbon atoms, an arylsilyl group of 6 to 20 carbon atoms, an alkylaryl group of 6 to 20 carbon atoms, an alkoxy group of 1 to 20 carbon atoms, an alkylsiloxy group of 1 to 20 carbon atoms, an aryloxy group of 6 to 20 carbon atoms, a halogen atom, an amino group and the mixtures thereof; Q is a divalent group selected from the group consisting of (CR 5 2) b, (SiR 5 2) b, (GeR 5 2) b, NR 5 and PR 5 for bridging R 1 S, wherein the substituent R 5 is independently a hydrogen atom, an alkyl radical of 1 to 20 carbon atoms, a cycloalkyl radical of 3 to 20 carbon atoms, an alkenyl radical of 1 to 20 carbon atoms, an aryl radical of 6 to 20 carbon atoms, an alkylaryl radical of 7 to 20 carbon atoms or arylalkyl radical of 7 to 20 carbon atoms, b is an integer of 1 to 4, when Q is (CR 5 2) b, (SiR 5 2) b or (GeR 5 2) b, the two substituents R 5 that are bonded to carbon, silicon(Si), germanium(Ge) can be connected with each other to form a ring of 2 to 7 carbon atoms, [Formula 2] M 1 R 2 m R 3 n R 4 p R 6 q In Formula 2, M 1 is an element selected from the group consisting of elements of Group 1, 2, 12, 13 and 14 of the Periodic Table, R 2, R 3, R 4 and R 6 are independently a hydrocarbyl group of 1 to 24 carbon atoms, an amide group, an alkoxy group or a halogen atom, m, n, p and q are independently 0 or 1, and m+n+p+q is equal to the valence of M 1, [Formula 3] M 2 R 7 r X s In Formula 3, M 2 is titanium(Ti), zirconium(Zr) or hafnium(Hf), R 7 is same as defined for R 1, X is a halogen atom, r is an integer of 0 or 1, s is an integer of 3 or 4, and r+s is equal to the valence of metal M 2.